Accessibility / Report Error

Freshwater mussels from South America: state of the art of Unionida, specially Rhipidodontini

Bivalves de água doce da América do Sul: estado da arte de Unionida, especialmente Rhipidodontini

Abstract

Unionida is the most diverse clade of freshwater bivalves. Among the groups occurring in South America, one with the highest number of species is Rhipidodontini (Hyriidae, Unionida, Paleoheterodonta, Bivalvia). However several issues remains on taxonomy and systematic of this group, leading to problems on species identification, description, as also as a limiting factor to other type of studies (e.g., ecology, conservation,…). In this paper is presented a synthesis of available knowledge about Diplodon Spix in Wagner, 1827 and Rhipidodonta Mörch, 1853 in South America, as a first step in order to a better understating of Rhipidodontini. The evaluation of different authors exposes the little agreement between them that resulted in a sort of divergent taxonomical opinions. Some comments on ecology, conservation and habitat preferences were made. This work can also encourage future research on taxonomy, systematic, ecology and conservation of freshwater mussels in South America.

Keywords:
Diplodon; Rhipidodonta; Hyriidae; Bivalvia; Freshwater bivalve

Resumo

Unionida é o clado mais diverso de bivalves de água doce. Entre os grupos que ocorrem na América do Sul, um dos com maior número de espécies é Rhipidodontini (Hyriidae, Unionida, Paleoheterodonta, Bivalvia). Porém, diversas questões taxonômicas e sistemáticas ainda incidem sob este grupo, levando a problemas de identificação de espécies, descrição, entre outros, como também tem atuado como limitador de outros tipos de estudos (e.g., ecologia, conservação,..). Neste trabalho é apresentada uma revisão do conhecimento acerca dos gêneros Diplodon Spix in Wagner, 1827 e Rhipidodonta Mörch, 1853 na América do Sul como um primeiro passo para a melhor compreensão de Rhipidodontini. Avaliando-se diferentes autores, se torna claro a pouca concordância entre eles, resultando em opiniões taxonômicas divergentes. São feitos também alguns comentários sobre ecologia, conservação e preferências ambientais. Este trabalho também deve encorajar futuros trabalhos sobre a taxonomia, sistemática, ecologia e conservação de bivalves de água na América do Sul.

Palavras-chave:
Diplodon; Rhipidodonta; Hyriidae; Bivalvia; Bivalve de água doce

Introduction

Mollusca is the second phylum in number of species, with estimates on the number of living species ranging up to 200,000 (Ponder & Lindberg 2008PONDER, W.F. & LINDBERG, D.R. 2008. Phylogeny and evolution of the Mollusca. University of California, California. 469p.). Bivalvia constitutes one of the most representative groups of this phylum with more than 8,000 species living worldwide. Although most are marine species, about 1,300 live in freshwater in all continents, except Antarctica (Ruppert et al. 2005RUPPERT, E.E., FOX, R.S. & BARNES, R.D. 2008. Zoologia dos Invertebrados – Uma abordagem funcional-evolutiva. Editora Roca. São Paulo., Bogan 2008BOGAN, A.E. 2008. Global diversity of freshwater mussels (Mollusca, Bivalvia) in freshwater. Hydrobiologia 595: 139-147.). Several lineages colonized freshwater ecosystems, especially the order Unionida (Paleoheterodonta), as well as some species of Arcida, Mytilida (Pteriomorpha), Venerida, Myida, and Anomalodesmata (Heterodonta), suggesting that bivalve invasions of freshwater environments occurred numerous times (Haag 2012HAAG, W.R. 2012. North American freshwater mussels: natural history, ecology and conservation. Cambridge University Press, Cambridge.). All living species of Unionida and Sphaeriidae (Heterodonta: Venerida) live exclusively in freshwater (Mansur 2007MANSUR, M.C.D. 2007. Moluscos da classe Bivalvia que tiveram sucesso ao se irradiarem no ambiente de água doce. 27-29p. In: Livro de Resumos do XX Encontro Brasileiro de Malacologia, Rio de Janeiro. 406pp., Giribet 2008GIRIBET, G. 2008. Bivalvia. In Phylogeny and evolution of the Mollusca (Ponder, W.F. & Lindberg, D.R., eds). University of Carolina Press, Berkeley, p.105-141.). Freshwater mussels (Unionida) are one of the most endangered animal group due to continuous degradation of their ecosystems (Strayer et al. 2004STRAYER, D.L., DOWINING, J.A., HAAG, W.R., KING, T.L., LAYZER, J.B., NEWTON, T.J. & NICHOLS, S.J. 2004. Changing perspectives on pearly mussels, North America’s most imperiled animals. Bioscience 54(5): 429-439., Amaral et al. 2008AMARAL, A.C.Z., RIBEIRO, C.V., MANSUR, M.C.D., SANTOS, S.B., AVELAR, W.E.P., MATTHEWS-CASCON, H., LEITE, F.P.P., MELO, G.A.S., COELHO, P.A., BUCKUP, G.B., BUCKUP, L., VENTURA, C.R.R. & TIAGO, C.G. 2008. A situação de ameaça dos invertebrados aquáticos no Brasil. In Livro vermelho da fauna brasileira ameaçada de extinção (Machado, A.B.M., Drummond, G.M. & Paglia, A.P., orgs). Ministério do Meio Ambiente, Brasilia, p. 156-301., Pereira et al. 2014PEREIRA, D., MANSUR, M.C.D., DUARTE, L.D.S., OLIVEIRA, A.S., PIMPÃO, D.M., CALLIL, C.T., ITUARTE, C., PARADA, E., PEREDO, S., DARRIGRAN, G., SCARABINO, F., CLAVIJO, C., LARA, G., MIYAHIRA, I.C., RODRIGUEZ, M.T.R. & LASSO, C. 2014. Bivalve distribution in hydrographic regions in South America: historical overview and conservation. Hydrobiologia 735(1): 15-44.). More recently Asian freshwater bivalves like Limnoperna fortunei (Dunker, 1857) (Mytilidae) and Corbicula spp. (Cyrenidae) that have been introduced to several distant countries and continents including South America caused severe ecological and economical loss (Darrigran & Damborenea 2006DARRIGRAN, G. & DAMBORENEA, C. 2006. Bio-invasión del mejillón dorado en el continente americano. Editorial de la Universidad de La Plata. La Plata, La Plata., Mansur et al. 2012MANSUR, M.C.D., SANTOS, C.P., PEREIRA, D., PAZ, I.C.P., ZURITA, M.L.L., RODRIGUEZ, M.T.R., NEHRKE, M.V. & BERGONCI, P.E.A. 2012. Moluscos límnicos invasores no Brasil: biologia, prevenção e controle. Redes Editora, Porto Alegre., Boltovskoy & Correa 2015BOLTOVSKOY, D. & CORREA, N. 2015. Ecosystem impacts of the invasive bivalve Limnoperna fortunei (golden mussel) in South America. Hydrobiologia 746: 81-95., Xu et al. 2015XU, M., DARRIGRAN, G., WANG, Z., ZHAO, N., LIN, CH & PAN, B. 2015. Experimental study on control of Limnoperna fortunei biofouling in water transfer tunnels. Journal of Hydro-environment Research 9(2): 248-258.).

Bivalves inhabit the bottom substrate, and are important members of freshwater communities performing important ecosystem services (Vaughn 2017VAUGHN, C.C. 2017. Ecosystem services provided by freshwater mussels. Hydrobiologia. DOI 10.1007/s10750-017-3139-x
https://doi.org/10.1007/s10750-017-3139-...
). Except for the environmental differences between marine and freshwater organisms, the freshwater species are generally similar to marine ones; although they are less colorful, camouflaged among sand grains and stones (Mansur 2007MANSUR, M.C.D. 2007. Moluscos da classe Bivalvia que tiveram sucesso ao se irradiarem no ambiente de água doce. 27-29p. In: Livro de Resumos do XX Encontro Brasileiro de Malacologia, Rio de Janeiro. 406pp.). Freshwater bivalves can be found in almost all available microhabitats, occupying different niches: burrowers of soft sediments (majority of species), burrowers of compacted sediments (e.g., Mycetopoda d’Orbigny, 1835 and Mycetopodella Marshall, 1928), wedgers of soft rocks and laterite (e.g., Bartlettia Adams, 1867), attached by byssus (e.g., Byssanodonta d’Orbigny, 1846 and Eupera Bourguignat, 1854) and species cemented to hard substrate (e.g., Acostaea d’Orbigny, 1851 and Etheria Lamarck, 1807) (Mansur 2007, 2012MANSUR, M.C.D. 2007. Moluscos da classe Bivalvia que tiveram sucesso ao se irradiarem no ambiente de água doce. 27-29p. In: Livro de Resumos do XX Encontro Brasileiro de Malacologia, Rio de Janeiro. 406pp., Haag 2012HAAG, W.R. 2012. North American freshwater mussels: natural history, ecology and conservation. Cambridge University Press, Cambridge., Pereira et al. 2014PEREIRA, D., MANSUR, M.C.D., DUARTE, L.D.S., OLIVEIRA, A.S., PIMPÃO, D.M., CALLIL, C.T., ITUARTE, C., PARADA, E., PEREDO, S., DARRIGRAN, G., SCARABINO, F., CLAVIJO, C., LARA, G., MIYAHIRA, I.C., RODRIGUEZ, M.T.R. & LASSO, C. 2014. Bivalve distribution in hydrographic regions in South America: historical overview and conservation. Hydrobiologia 735(1): 15-44.).

Our main goal was to summarize the knowledge about Unionida (Bivalvia, Paleoheterodonta) in South America, especially regarding Rhipidodontini (Hyriidae).

1. Systematics of Unionida

The taxonomic instability of bivalves results, in part, from the large amount of available names (Bieler & Mikkelsen 2006BIELER, R. & MIKKELSEN, A.P.M. 2006. Bivalvia – a look at the branches. Zool. J. Linnean Soc. 148: 223-235.), which change according to the different characters emphasized by each author. The systematic of Bivalvia was addressed by several authors (Thiele 1934THIELE, J. 1934. Handbuch der systematischen Weichtierkunde – part 3 (Scaphopoda/Bivalvia/Cephalopoda). 779-1022p. (in German, English translation by Bieler, R. & Mikkelsen, P.M. 1998. Handbook of systematic malacology – part 3 and 4. Smithsonian Institution Libraries, Washington D.C. p. 1193-1690)., Newell 1965NEWELL, N.D. 1965. The classification of the Bivalvia. Am. Mus. Novit .2206: 1-25., Cox et al. 1969COX, L.R., NEWELL, N.D., BOYD, D.W., BRANSON, C.C., CASEY, R., CHAVAN, A., COOGAN, A.H., DECHASEAUX, C., FLEMING, C.A., HAAS, F., HERTLEIN, L.G., KAUFFMAN, E.G., KEEN, A.M., LAROCQUE, A., MCALESTER, A.L., MOORE, R.C., NUTTALL, C.P., PERKINS, B.F., PURI, H.S., SMITH, L.A., SOOT-RYEN, T., STENZEL, H.B., TRUEMAN, E.R., TURNER, R.D. & WEIR, J. 1969. Treatise on Invertebrate Paleontology – Part N, Volume 1 (of 3), Mollusca 6, Bivalvia. The Geological Society of America, Inc. and The University of Kansas. Kansas., Franc 1960FRANC, 1960. Classe des Bivalves. In: Traité de Zoologie – Tome V, Fascicule II (Grassé, P.P., Ed.) Masson et cie Éditeurs, Paris. p.1855-2164p., Schneider 2001SCHNEIDER, J.A. 2001. Bivalve systematics during the 20th century. J. Paleo. 75(6): 1119-1127., Giribet 2008GIRIBET, G. 2008. Bivalvia. In Phylogeny and evolution of the Mollusca (Ponder, W.F. & Lindberg, D.R., eds). University of Carolina Press, Berkeley, p.105-141.) and the position of Paleoheterodonta remains quite stable. Paleoheterodonta is usually presented as a “halfway” between Pteriomorphia and Heterodonta (Schneider 2001SCHNEIDER, J.A. 2001. Bivalve systematics during the 20th century. J. Paleo. 75(6): 1119-1127., Giribet 2008GIRIBET, G. 2008. Bivalvia. In Phylogeny and evolution of the Mollusca (Ponder, W.F. & Lindberg, D.R., eds). University of Carolina Press, Berkeley, p.105-141.). Bieler et al. (2014)BIELER, R., MIKKELSEN, P.M.; COLLINS, T.M., GLOVER, E.A., GONZÁLEZ, V.L., GRAF, D.L., HARPER, E.M., HEALY, J., KAWAUCHI, G.Y., SHARMA, P.P., STAUBACH, S., STRONG, E.E., TAYLOR, J.D., TËMKIN, I., ZARDUS, J.D., CLARK, S., GUZMÁN, A., McINTYRE, E., SHARP, P. & GIRIBET, G. 2014. Investigating the Bivalve Tree of Life – an exemplar-based approach combining molecular and novel morphological characters. Invertebrate Systematics 28: 32-115. presented a slightly different arrangement where Paleoheterodonta is sister group to Archiheterodonta, and this is sister to a clade composed by Anomalodesmata + Imparidentia, that embraces most bivalves previously in Heterodonta. Unionida is included in Paleoheterodonta and it is a group of usually large-sized mussels that have a peculiar life cycle with a parasitic stage and presents the most successful radiation in freshwaters by bivalves (Graf & Cummings 2006GRAF, D.L. & CUMMINGS, K.S. 2006. Paleoheterodont diversity (Mollusca: Trigonoida + Unionoida): what we know and what we wish we knew about freshwater mussel evolution. Zool. J. Linnean Soc. 148: 343-394., Haag 2012HAAG, W.R. 2012. North American freshwater mussels: natural history, ecology and conservation. Cambridge University Press, Cambridge.).

The inner relationships of Unionida are not as clear as the position of Paleoheterodonta. Simpson (1914)SIMPSON, C.T. 1914. A descriptive catalogue of the Naiades or pearly freshwater mussels. Privately published by Bryant Walker, Michigan. proposed only two families in Unionoida (= Unionida): Unionidae and Mutelidae. Most bivalves that are currently recognized as Unionidae, Margaritiferidae and Hyriidae (Figure 1A-C) compose the first group; and the current representatives of Mycetopodidae and Iridinidae are part of the second group (Figure 1D-E). Therefore, Unionidae sensuSimpson (1914)SIMPSON, C.T. 1914. A descriptive catalogue of the Naiades or pearly freshwater mussels. Privately published by Bryant Walker, Michigan. encompasses the species with larvae of glochidium type, whereas Mutelidae sensuSimpson (1914)SIMPSON, C.T. 1914. A descriptive catalogue of the Naiades or pearly freshwater mussels. Privately published by Bryant Walker, Michigan., those with the lasidium type. Ortmann (1921)ORTMANN, A.E. 1921. South American naiades, a contribution to the knowledge of the fresh-water mussels of South America. Mem. Carnegie Mus. 8(3): 451-670. recognized three families within the superfamily Naiades: Margaritanidae (= Margaritiferidae), Unionidae and Mutelidae (= Hyriidae + Mycetopodidae + Iridinidae). Based on morphological characteristics of their soft parts, not only on their shells, Ortmann (1911ORTMANN, A.E. 1911. The anatomical structure of certain exotic naiades compared with that of the North American forms. Nautilus 24: 103-131., 1921ORTMANN, A.E. 1921. South American naiades, a contribution to the knowledge of the fresh-water mussels of South America. Mem. Carnegie Mus. 8(3): 451-670.) noted similarities between hyriids and mutelids, and removed hyriids from Unionidae, establishing them as a subfamily of Mutelidae.

Figure 1
Members of Unionida. A – Unionidae, Lampsilis fasciola Rafinesque, 1820, MNRJ (Museu Nacional do Rio de Janeiro) 7468; B – Margaritiferidae, Margaritifera sp., MNRJ 32868; C - Echyridella menziesii (Dieffenbach, 1843), MNRJ 4374; D – Iridinidae, Aspatharia pfeifferiana (Bernardi, 1860), MNRJ HSL 6328; E – Mycetopodidae, Mycetopoda soleniformis d’Orbigny, 1835, MNRJ 3841; F – Etheriidae, Etheria elliptica Lamarck, 1807, MNRJ HSL 6111. Scale bar = 1 cm.

Thiele (1934)THIELE, J. 1934. Handbuch der systematischen Weichtierkunde – part 3 (Scaphopoda/Bivalvia/Cephalopoda). 779-1022p. (in German, English translation by Bieler, R. & Mikkelsen, P.M. 1998. Handbook of systematic malacology – part 3 and 4. Smithsonian Institution Libraries, Washington D.C. p. 1193-1690). classified all freshwater mussels as Unionacea, recognizing four families: Margaritanidae, Unionidae, Mutelidae, and Aetheriidae (Figure 1). That is the first classification scheme that posed an exclusive family for freshwater oysters (Aetheriidae = Etheriidae) (Figure 1F). Thiele (1934)THIELE, J. 1934. Handbuch der systematischen Weichtierkunde – part 3 (Scaphopoda/Bivalvia/Cephalopoda). 779-1022p. (in German, English translation by Bieler, R. & Mikkelsen, P.M. 1998. Handbook of systematic malacology – part 3 and 4. Smithsonian Institution Libraries, Washington D.C. p. 1193-1690). used the same subfamilies of Mutelidae proposed by Ortmann (1921)ORTMANN, A.E. 1921. South American naiades, a contribution to the knowledge of the fresh-water mussels of South America. Mem. Carnegie Mus. 8(3): 451-670..

These first arrangements of Unionida follow biogeographical patterns: Boreal species grouped in Margaritiferidae (or Margaritanidae) and Unionidae; and Austral species in Mutelidae (= Hyriidae + Mycetopodidae) (Ortmann 1921ORTMANN, A.E. 1921. South American naiades, a contribution to the knowledge of the fresh-water mussels of South America. Mem. Carnegie Mus. 8(3): 451-670., Thiele 1934THIELE, J. 1934. Handbuch der systematischen Weichtierkunde – part 3 (Scaphopoda/Bivalvia/Cephalopoda). 779-1022p. (in German, English translation by Bieler, R. & Mikkelsen, P.M. 1998. Handbook of systematic malacology – part 3 and 4. Smithsonian Institution Libraries, Washington D.C. p. 1193-1690).). However, the separation is not clear cut, for example, Thiele (1934)THIELE, J. 1934. Handbuch der systematischen Weichtierkunde – part 3 (Scaphopoda/Bivalvia/Cephalopoda). 779-1022p. (in German, English translation by Bieler, R. & Mikkelsen, P.M. 1998. Handbook of systematic malacology – part 3 and 4. Smithsonian Institution Libraries, Washington D.C. p. 1193-1690). left Virgus Simpson, 1900 and other austral insular species of Oceania in Unionidae.

Modell (1942)MODELL, H. 1942. Das natürliche system der najaden. Archiv für Molluskenkunde 74(5/6): 161-191. (in German, English translation in Stansberry, D.H. & Soehngen, U. 1964. Sterkiana 14: 1-18). proposed four families (Mutelidae, Elliptionidae, Margaritiferidae, and Unionidae) with many subfamilies. Elliptionidae comprises the majority of species traditionally allocated in Unionidae. Modell (1942)MODELL, H. 1942. Das natürliche system der najaden. Archiv für Molluskenkunde 74(5/6): 161-191. (in German, English translation in Stansberry, D.H. & Soehngen, U. 1964. Sterkiana 14: 1-18). also suggested a relationship between this group and Mutelidae, wherein all lasidium bearers were grouped together. Modell (1942)MODELL, H. 1942. Das natürliche system der najaden. Archiv für Molluskenkunde 74(5/6): 161-191. (in German, English translation in Stansberry, D.H. & Soehngen, U. 1964. Sterkiana 14: 1-18). as Simpson (1914)SIMPSON, C.T. 1914. A descriptive catalogue of the Naiades or pearly freshwater mussels. Privately published by Bryant Walker, Michigan., placed hyriids within Unionidae. According to Modell (1942)MODELL, H. 1942. Das natürliche system der najaden. Archiv für Molluskenkunde 74(5/6): 161-191. (in German, English translation in Stansberry, D.H. & Soehngen, U. 1964. Sterkiana 14: 1-18)., Mutelidae is a basal group that originates all other mussels.

Parodiz & Bonetto (1963)PARODIZ, J.J. & BONETTO, A.A. 1963. Taxonomy and Zoogeography relationships of the South American naiads (Pelecypoda: Unionacea and Mutelacea). Malacologia 1: 179-213. proposed an arrangement in two superfamilies based mainly on the larval type, which was widely accepted by subsequent authors: Unionacea (Unionidae + Margaritiferidae + Hyriidae) with glochidium larva; and Mutelacea (Mutelidae + Mycetopodidae) with lasidium larva. Etheriidae is not included in the classification, as its larval stage was unknown at that time (Bogan & Roe 2008BOGAN, A.E. & ROE, K.J. 2008. Freshwater bivalve (Unioniformes) diversity, systematics, and evolution: status and future directions. J. North Am. Benthol. Soc. 27(2):349-369.). The larval stage of Acostaea rivolii (Deshayes, 1827) (Etheriidae) was later identified as a lasidium (Arteaga-Sogamoso 1994ARTEAGA-SOGAMOSO, E. 1994. El lasidium de Acostaea rivoli Deshayes, 1827 (Mollusca; Bivalvia-Etheriidae) y su importancia para la ubicación taxonômica de esta espécie. Bol. ecotropica 27: 1-9., Bonetto, 1997BONETTO, A.A. 1997. Las “ostras de agua dulce” (Muteloidea: Mutelidae). Su taxonomía y distribución geográfica en el conjunto de las naiades del mundo. Biociências 5(1): 113-142.). Kabat (1997)KABAT, A.R. 1997. Correct family names for the freshwater “Muteloid” bivalves (Unionoida: Etherioidea). Occas. pap. mollusks 5(72): 379-392. revised the names used in Unionida claiming that Etherioidea and Iridinidae should be used instead of Muteloidea and Mutelidae. The recent works accepted these suggestions (e.g.,Graf & Cummings 2007GRAF, D.L. & CUMMINGS, K.S. 2007. Review of the systematic and global diversity of freshwater mussel species (Bivalvia: Unionoida). J. Mollus. Stud. 73: 291-314.).

In the beginning of the 21st century, there has been a reevaluation of systematic relationships based on phylogenetic methodologies, including molecular data in some of these analyses. The monophyly of Etheriidae was questioned by Bogan & Hoeh (2000)BOGAN, A.E. & HOEH, W.R. 2000. On becoming cemented: evolutionary relationships among the genera in the freshwater familiy Etheriidae (Bivalvia: Unionoida). In The evolutionary biology of the Bivalvia (Harper, E.M.; Taylor, J.D. & Crame, J., eds). Geological Society, London, London, p.159-168. who considered Acostea and Etheria (traditionally included in Etheriidae) within Mycetopodidae and, Pseudomulleria Anthony, 1907, an Indian freshwater oyster, inside Unionidae. Bogan & Hoeh (2000)BOGAN, A.E. & HOEH, W.R. 2000. On becoming cemented: evolutionary relationships among the genera in the freshwater familiy Etheriidae (Bivalvia: Unionoida). In The evolutionary biology of the Bivalvia (Harper, E.M.; Taylor, J.D. & Crame, J., eds). Geological Society, London, London, p.159-168. proposed multiple origins to cementation among freshwater bivalves, arguing the occurrence of the same process in the non-related Cyrenidae, Posostrea anomioides Bogan & Bouchet, 1998. The analysis of Hoeh et al. (2001)HOEH, W.R., BOGAN, A.E. & HEARD, W.H. 2001. A phylogenetic perspective on the evolution of morphological and reproductive characteristics in the Unionoida. In: Bauer, G. & Wächtler, K. (eds.) Evolution of the freshwater mussels Unionoida. Springer-Verlag, Berlin. is similar to Bogan & Hoeh (2000)BOGAN, A.E. & HOEH, W.R. 2000. On becoming cemented: evolutionary relationships among the genera in the freshwater familiy Etheriidae (Bivalvia: Unionoida). In The evolutionary biology of the Bivalvia (Harper, E.M.; Taylor, J.D. & Crame, J., eds). Geological Society, London, London, p.159-168., suggesting that Hyriidae is a sister group to the remaining Unionida and considering Unionacea (sensuParodiz & Bonetto, 1963PARODIZ, J.J. & BONETTO, A.A. 1963. Taxonomy and Zoogeography relationships of the South American naiads (Pelecypoda: Unionacea and Mutelacea). Malacologia 1: 179-213.) as a paraphyletic group. That scheme implies that the glochidium and the larvae incubation in the inner demibranch (endogenous) are plesiomorphic characteristics of Unionida.

Graf (2000)GRAF, D.L. 2000. The Etherioidea revisited: a phylogenetic analysis of Hyriid relationships (Mollusca: Bivalvia: Paleoheterodonta: Unionoida). Occas. pap. Mus. Zool. Univ. Mich. 729: 1-21. analyzed the relationships inside Etherioidea, with an emphasis on Hyriidae; suggesting that Hyriidae, Iridinidae and Etheriidae are monophyletic. Unionidae, once more had its monophyly questioned and Grandidieria Bourguignat, 1885, traditionally placed in Unionidae is considered a sister group of Etherioidea. Graf & Cummins (2006) suggested that Paleoheterodonta is monophyletic and divided Unionoida in two clades: Unionoidea (Unionidae + Margaratiferidae) and Etherioidea (Hyriidae + Etheriidae + Mycetopodidae + Iridinidae). Unlike other authors (e.g.,Bogan & Hoeh, 2000BOGAN, A.E. & HOEH, W.R. 2000. On becoming cemented: evolutionary relationships among the genera in the freshwater familiy Etheriidae (Bivalvia: Unionoida). In The evolutionary biology of the Bivalvia (Harper, E.M.; Taylor, J.D. & Crame, J., eds). Geological Society, London, London, p.159-168.; Hoeh et al. 2001HOEH, W.R., BOGAN, A.E. & HEARD, W.H. 2001. A phylogenetic perspective on the evolution of morphological and reproductive characteristics in the Unionoida. In: Bauer, G. & Wächtler, K. (eds.) Evolution of the freshwater mussels Unionoida. Springer-Verlag, Berlin.), Graf & Cummings (2006)GRAF, D.L. & CUMMINGS, K.S. 2006. Paleoheterodont diversity (Mollusca: Trigonoida + Unionoida): what we know and what we wish we knew about freshwater mussel evolution. Zool. J. Linnean Soc. 148: 343-394. suggested the monophyly of Unionidae and Etheriidae, condition latter also supported by Whelan et al. (2011)WHELAN, N.V., GENEVA, A.J. & GRAF, D.L. 2011. Molecular phylogenetics analysis of tropical freshwater mussels (Mollusca: Bivalvia: Unionoida) resolves the position of Coelatura and supports a monophyletic Unionidae. Mol. Phylogenet. Evol. 61(2): 504-514.. In that scheme, Unionoidea is the basal group of Unionida, while Hyriidae is the basal group of Etherioidea. In certain aspects, this arrangement is a return to early schemes of systematic organization (e.g.,Ortmann, 1921ORTMANN, A.E. 1921. South American naiades, a contribution to the knowledge of the fresh-water mussels of South America. Mem. Carnegie Mus. 8(3): 451-670.) with boreal species separated from the austral species. The exceptions are some austral species of Unionidae (Haas 1969HAAS, F. 1969. Superfamilia Unionacea. In Das Tierrich, Lieferung – vol 88 (Martens, R., Hennig W. & Wermuth, H., ed.). Walter de Gruyter and Co., Berlin., Graf & Cummings 2007GRAF, D.L. & CUMMINGS, K.S. 2007. Review of the systematic and global diversity of freshwater mussel species (Bivalvia: Unionoida). J. Mollus. Stud. 73: 291-314.).

Nevesskaja (2009)NEVESSKAJA, L.A. 2009. Principle of systematics and the system of Bivalves. Paleontol. J. 43(1): 1-11. recognized two groups of living freshwater mussels: Unionoidea (Unionidae + Margaratiferidae) and Etherioidea (Mutelidae + Etheriidae), but did not list the genera within each group, so it is impossible to know precisely where Hyriidae and Mycetopodidae stand. As Mutelidae traditionally embrace the species of Iridinidae, Mycetopodidae and Hyriidae (Ortmann 1921ORTMANN, A.E. 1921. South American naiades, a contribution to the knowledge of the fresh-water mussels of South America. Mem. Carnegie Mus. 8(3): 451-670., Thiele 1934THIELE, J. 1934. Handbuch der systematischen Weichtierkunde – part 3 (Scaphopoda/Bivalvia/Cephalopoda). 779-1022p. (in German, English translation by Bieler, R. & Mikkelsen, P.M. 1998. Handbook of systematic malacology – part 3 and 4. Smithsonian Institution Libraries, Washington D.C. p. 1193-1690)., Graf 2000GRAF, D.L. 2000. The Etherioidea revisited: a phylogenetic analysis of Hyriid relationships (Mollusca: Bivalvia: Paleoheterodonta: Unionoida). Occas. pap. Mus. Zool. Univ. Mich. 729: 1-21.); we can suppose that Nevesskaja (2009)NEVESSKAJA, L.A. 2009. Principle of systematics and the system of Bivalves. Paleontol. J. 43(1): 1-11. considered all the species of these families as belonging to Mutelidae.

A major point of disagreement between different authors is the position of Hyriidae, sometimes grouped with glochidium-bearing species, and sometimes grouped with the other Gondwanic species (Mycetopodidae and Etheriidae) (Bogan & Hoeh 2000BOGAN, A.E. & HOEH, W.R. 2000. On becoming cemented: evolutionary relationships among the genera in the freshwater familiy Etheriidae (Bivalvia: Unionoida). In The evolutionary biology of the Bivalvia (Harper, E.M.; Taylor, J.D. & Crame, J., eds). Geological Society, London, London, p.159-168., Graf 2000GRAF, D.L. 2000. The Etherioidea revisited: a phylogenetic analysis of Hyriid relationships (Mollusca: Bivalvia: Paleoheterodonta: Unionoida). Occas. pap. Mus. Zool. Univ. Mich. 729: 1-21., Graf & Cummings 2006GRAF, D.L. & CUMMINGS, K.S. 2006. Paleoheterodont diversity (Mollusca: Trigonoida + Unionoida): what we know and what we wish we knew about freshwater mussel evolution. Zool. J. Linnean Soc. 148: 343-394., Bogan 2008BOGAN, A.E. 2008. Global diversity of freshwater mussels (Mollusca, Bivalvia) in freshwater. Hydrobiologia 595: 139-147.). Bieler et al. (2010)BIELER, R., CARTER, J.G. COAN, E.V. 2010. Classification of bivalve families. Malacologia 52(2): 113-184. adopted an intermediate solution to the problem, dividing the living species of Unionida in three superfamilies (Table 1). In this classification, Hyrioidea (represented only by Hyriidae) occupy an intermediate position between the two other groups, Etherioidea and Unionoidea, reflecting the conflicting data from other authors concerning the position of Hyriidae (Bogan & Hoeh 2000BOGAN, A.E. & HOEH, W.R. 2000. On becoming cemented: evolutionary relationships among the genera in the freshwater familiy Etheriidae (Bivalvia: Unionoida). In The evolutionary biology of the Bivalvia (Harper, E.M.; Taylor, J.D. & Crame, J., eds). Geological Society, London, London, p.159-168., Hoeh et al. 2001HOEH, W.R., BOGAN, A.E. & HEARD, W.H. 2001. A phylogenetic perspective on the evolution of morphological and reproductive characteristics in the Unionoida. In: Bauer, G. & Wächtler, K. (eds.) Evolution of the freshwater mussels Unionoida. Springer-Verlag, Berlin., Graf & Cummins 2006, 2007). Graf et al. (2015)GRAF, D.L., JONES, H., GENEVA, A.J.; PFEIFER III, J.M. & KLUNZINGER, M.W. 2015. Molecular phylogenetics analysis supports a Gondwanan origin of the Hyriidae (Mollusca: Bivalvia: Unionoida) and the paraphyly of Australasian taxa. Mol. Phylogenet. Evol. 85: 1-9. presented Hyriidae as sister to all other freshwater mussel families, in a position quite different from the previously one (Graf & Cummings 2006GRAF, D.L. & CUMMINGS, K.S. 2006. Paleoheterodont diversity (Mollusca: Trigonoida + Unionoida): what we know and what we wish we knew about freshwater mussel evolution. Zool. J. Linnean Soc. 148: 343-394.), however similar (regarding to Hyriidae position) to topology presented by Bogan & Hoeh (2000)BOGAN, A.E. & HOEH, W.R. 2000. On becoming cemented: evolutionary relationships among the genera in the freshwater familiy Etheriidae (Bivalvia: Unionoida). In The evolutionary biology of the Bivalvia (Harper, E.M.; Taylor, J.D. & Crame, J., eds). Geological Society, London, London, p.159-168. and Hoeh et al. (2009)HOEH, W.R., BOGAN, A.E., HEARD, W.H. & CHAPMAN, E.G., 2009. Paleoheterodont phylogeny, character evolution, diversity and phylogenetic classification: a reflection of method of analysis. Malacologia 51: 307-317..

Table 1
Relationships of Paleoheterodonta, following Bieler et al. (2010)BIELER, R., CARTER, J.G. COAN, E.V. 2010. Classification of bivalve families. Malacologia 52(2): 113-184., modified to include only the living taxa of Paleoheterodonta.

2. Geographical distribution of South American mussels

Unionida occurs worldwide in different kinds of freshwater habitats except in Antarctica (Graf & Cummings 2006GRAF, D.L. & CUMMINGS, K.S. 2006. Paleoheterodont diversity (Mollusca: Trigonoida + Unionoida): what we know and what we wish we knew about freshwater mussel evolution. Zool. J. Linnean Soc. 148: 343-394., Bogan 2008BOGAN, A.E. 2008. Global diversity of freshwater mussels (Mollusca, Bivalvia) in freshwater. Hydrobiologia 595: 139-147.). Current estimates recognize approximately 900 species distributed among six families: Hyriidae, Mycetopodidae, Unionidae, Iridinidae and Etheriidae (Graf & Cummings 2006GRAF, D.L. & CUMMINGS, K.S. 2006. Paleoheterodont diversity (Mollusca: Trigonoida + Unionoida): what we know and what we wish we knew about freshwater mussel evolution. Zool. J. Linnean Soc. 148: 343-394., 2007GRAF, D.L. & CUMMINGS, K.S. 2007. Review of the systematic and global diversity of freshwater mussel species (Bivalvia: Unionoida). J. Mollus. Stud. 73: 291-314., Bieler et al. 2010BIELER, R., CARTER, J.G. COAN, E.V. 2010. Classification of bivalve families. Malacologia 52(2): 113-184.).

Etheriidae is Gondwanic and comprises four species, occurring in Africa, Etheria elliptica Lamarck, 1807; India, Pseudomulleria dalyi (Smith, 1898) and South America, Acostea rivolii and Bartlettia stefanensis (Moricand, 1856) (Haas 1969HAAS, F. 1969. Superfamilia Unionacea. In Das Tierrich, Lieferung – vol 88 (Martens, R., Hennig W. & Wermuth, H., ed.). Walter de Gruyter and Co., Berlin., Graf & Cummings 2006GRAF, D.L. & CUMMINGS, K.S. 2006. Paleoheterodont diversity (Mollusca: Trigonoida + Unionoida): what we know and what we wish we knew about freshwater mussel evolution. Zool. J. Linnean Soc. 148: 343-394., 2007GRAF, D.L. & CUMMINGS, K.S. 2007. Review of the systematic and global diversity of freshwater mussel species (Bivalvia: Unionoida). J. Mollus. Stud. 73: 291-314.). The monophyly of this family is disputed and there is no agreement as highlighted by different opinions available (Parodiz & Bonetto 1963PARODIZ, J.J. & BONETTO, A.A. 1963. Taxonomy and Zoogeography relationships of the South American naiads (Pelecypoda: Unionacea and Mutelacea). Malacologia 1: 179-213., Bogan & Hoeh 2000BOGAN, A.E. & HOEH, W.R. 2000. On becoming cemented: evolutionary relationships among the genera in the freshwater familiy Etheriidae (Bivalvia: Unionoida). In The evolutionary biology of the Bivalvia (Harper, E.M.; Taylor, J.D. & Crame, J., eds). Geological Society, London, London, p.159-168., Bonetto 1997BONETTO, A.A. 1997. Las “ostras de agua dulce” (Muteloidea: Mutelidae). Su taxonomía y distribución geográfica en el conjunto de las naiades del mundo. Biociências 5(1): 113-142., Simone 2006SIMONE, L.R.L. 2006. Land and freshwater molluscs of Brazil. EGB, Fapesp, São Paulo. 390pp., Hoeh et al 2009HOEH, W.R., BOGAN, A.E., HEARD, W.H. & CHAPMAN, E.G., 2009. Paleoheterodont phylogeny, character evolution, diversity and phylogenetic classification: a reflection of method of analysis. Malacologia 51: 307-317., Mansur et al. 2012MANSUR, M.C.D., SANTOS, C.P., PEREIRA, D., PAZ, I.C.P., ZURITA, M.L.L., RODRIGUEZ, M.T.R., NEHRKE, M.V. & BERGONCI, P.E.A. 2012. Moluscos límnicos invasores no Brasil: biologia, prevenção e controle. Redes Editora, Porto Alegre.).

Mycetopodidae is Neotropical distributed all over South America east of the Andes and west of Central America all the way to Mexico (Graf & Cummings 2006GRAF, D.L. & CUMMINGS, K.S. 2006. Paleoheterodont diversity (Mollusca: Trigonoida + Unionoida): what we know and what we wish we knew about freshwater mussel evolution. Zool. J. Linnean Soc. 148: 343-394., Bogan 2008BOGAN, A.E. 2008. Global diversity of freshwater mussels (Mollusca, Bivalvia) in freshwater. Hydrobiologia 595: 139-147.). There are about 30 valid species of Mycetopodidae in 12 (Simone 2006SIMONE, L.R.L. 2006. Land and freshwater molluscs of Brazil. EGB, Fapesp, São Paulo. 390pp.) or 11 genera (Graf & Cummings 2007GRAF, D.L. & CUMMINGS, K.S. 2007. Review of the systematic and global diversity of freshwater mussel species (Bivalvia: Unionoida). J. Mollus. Stud. 73: 291-314.). Bonetto (1997)BONETTO, A.A. 1997. Las “ostras de agua dulce” (Muteloidea: Mutelidae). Su taxonomía y distribución geográfica en el conjunto de las naiades del mundo. Biociências 5(1): 113-142. also includes Acostaea in Mycetopodidae, whereas other authors (Parodiz & Bonetto 1963PARODIZ, J.J. & BONETTO, A.A. 1963. Taxonomy and Zoogeography relationships of the South American naiads (Pelecypoda: Unionacea and Mutelacea). Malacologia 1: 179-213., Graf 2000GRAF, D.L. 2000. The Etherioidea revisited: a phylogenetic analysis of Hyriid relationships (Mollusca: Bivalvia: Paleoheterodonta: Unionoida). Occas. pap. Mus. Zool. Univ. Mich. 729: 1-21.) believe that Leila Gray, 1840, usually placed in Mycetopodidae, belongs to Iridinidae. The origin of Mycetopodidae is in the Cretaceous (Cox et al. 1969COX, L.R., NEWELL, N.D., BOYD, D.W., BRANSON, C.C., CASEY, R., CHAVAN, A., COOGAN, A.H., DECHASEAUX, C., FLEMING, C.A., HAAS, F., HERTLEIN, L.G., KAUFFMAN, E.G., KEEN, A.M., LAROCQUE, A., MCALESTER, A.L., MOORE, R.C., NUTTALL, C.P., PERKINS, B.F., PURI, H.S., SMITH, L.A., SOOT-RYEN, T., STENZEL, H.B., TRUEMAN, E.R., TURNER, R.D. & WEIR, J. 1969. Treatise on Invertebrate Paleontology – Part N, Volume 1 (of 3), Mollusca 6, Bivalvia. The Geological Society of America, Inc. and The University of Kansas. Kansas.).

There are around 80 species of Hyriidae, occurring throughout Oceania and South America, with only two or three species west of the Andes (Bonetto et al. 1986BONETTO, A.A., TASSARA, M.P. & RUMI, A. 1986. Australis n. subgen. de Diplodon Spix (Bivalvia, Unionacea) y posibles relaciones con Hyriidae australianos. Bol. Soc. Biol. Concepc. 57: 55-61.; Parada & Peredo, 2002PARADA, E. & PEREDO, S. 2002. Estado actual de la taxonomía de bivalvos dulceacuícolas chilenos: progresos y conflictos. Rev. Chil. Hist. Nat. 75: 691-701.; Graf & Cummings, 2007GRAF, D.L. & CUMMINGS, K.S. 2007. Review of the systematic and global diversity of freshwater mussel species (Bivalvia: Unionoida). J. Mollus. Stud. 73: 291-314.; Bogan, 2008BOGAN, A.E. 2008. Global diversity of freshwater mussels (Mollusca, Bivalvia) in freshwater. Hydrobiologia 595: 139-147.). Hyriidae is monophyletic (Graf et al. 2015GRAF, D.L., JONES, H., GENEVA, A.J.; PFEIFER III, J.M. & KLUNZINGER, M.W. 2015. Molecular phylogenetics analysis supports a Gondwanan origin of the Hyriidae (Mollusca: Bivalvia: Unionoida) and the paraphyly of Australasian taxa. Mol. Phylogenet. Evol. 85: 1-9.) and usually divided in two groups (sub-families), the Hyriinae, which comprises South American species, except by Hyridella Swainson, 1840 and some related Australian species; and Velesunioninae, that comprises most Australian species (Graf & Cummings, 2006GRAF, D.L. & CUMMINGS, K.S. 2006. Paleoheterodont diversity (Mollusca: Trigonoida + Unionoida): what we know and what we wish we knew about freshwater mussel evolution. Zool. J. Linnean Soc. 148: 343-394., 2007GRAF, D.L. & CUMMINGS, K.S. 2007. Review of the systematic and global diversity of freshwater mussel species (Bivalvia: Unionoida). J. Mollus. Stud. 73: 291-314.; Bieler et al. 2010BIELER, R., CARTER, J.G. COAN, E.V. 2010. Classification of bivalve families. Malacologia 52(2): 113-184.; Graf et al. 2015GRAF, D.L., JONES, H., GENEVA, A.J.; PFEIFER III, J.M. & KLUNZINGER, M.W. 2015. Molecular phylogenetics analysis supports a Gondwanan origin of the Hyriidae (Mollusca: Bivalvia: Unionoida) and the paraphyly of Australasian taxa. Mol. Phylogenet. Evol. 85: 1-9.). Among Hyriidae seven genera are recognized to South America: Prisodon Schumacher, 1817; Paxyodon Schumacher, 1817; Callonaia Simpson, 1900; Castalia Lamarck, 1819; Castaliella Simpson, 1900; Diplodon Spix in Wagner, 1827 and Rhipidodonta Mörch, 1893 (Simone, 2006SIMONE, L.R.L. 2006. Land and freshwater molluscs of Brazil. EGB, Fapesp, São Paulo. 390pp.); and, nine genera to Australia: Hyridella; Cucumerunio Iredale, 1934; Echyridella McMichael & Hiscock, 1958; Virgus; Velesunio Iredale, 1934; Alathyria Iredale, 1934; Lortilella Iredale, 1934; Microdontia Tapparone Canefri, 1883; Westralunio Iredale, 1934 (Graf & Cummings, 2007GRAF, D.L. & CUMMINGS, K.S. 2007. Review of the systematic and global diversity of freshwater mussel species (Bivalvia: Unionoida). J. Mollus. Stud. 73: 291-314.). It is noteworthy that not all authors agree with the valid status of each of these genera. Simone (2006)SIMONE, L.R.L. 2006. Land and freshwater molluscs of Brazil. EGB, Fapesp, São Paulo. 390pp. considered Triplodon Spix in Wagner, 1827 as synonym, unlike Mansur & Pimpão (2008)MANSUR, M.C.D. & PIMPÃO, D.M. 2008. Triplodon chodo, a new species of species of pearly fresh water mussel from Amazon Basin (Mollusca: Bivalvia: Unionoida: Hyriidae). Rev. Bras. Zool. 25(1): 111-115. who described a new species of this genus. The oldest Hyriidae record is from Triassic of New Zealand (Campbell et al. 2003CAMPBELL, J.D., COOMBS, D.S. & GREBNEFF, A. 2003. Willsher group and geology of the Triassic Kaka Point coastal section, south-east Otago, New Zeland. J. R. Soc. N. Z. 33: 7-38.) and from Jurassic of South America (Perea et al. 2009PEREA, D., SOTO, M., VEROSLAVSKY, G., MARÍNEZ, S. & UBILA, M., 2009. A Late Jurassic fóssil assemblage in Gondwana: biostratigraphy and correlations of the Tacuarembó Formation, Parana Basin, Uruguay. J. S. Am. Earth Sci. 28, 168–179). Molecular clock indicated a Gondwanan origin of Hyriidae (Graf et al. 2015GRAF, D.L., JONES, H., GENEVA, A.J.; PFEIFER III, J.M. & KLUNZINGER, M.W. 2015. Molecular phylogenetics analysis supports a Gondwanan origin of the Hyriidae (Mollusca: Bivalvia: Unionoida) and the paraphyly of Australasian taxa. Mol. Phylogenet. Evol. 85: 1-9.; Santos-Neto et al. 2016SANTOS-NETO, G.C., BEASLEY, C.R., SCHNEIDER, H., PIMPÃO, D.M., HOEH, W.R., SIMONE, L.R.L. & TAGLIARO, C.H. 2016. Genetic relationships among freshwater mussel species from fifteen Amazonian rivers and inferences on the evolution of the Hyriidae (Mollusca: Bivalvia: Unionoida). Mol. Phylogenet. Evol. 100: 148-159.).

The Figures 2 to 4, based on the data available in Graf & Cummings (2007)GRAF, D.L. & CUMMINGS, K.S. 2007. Review of the systematic and global diversity of freshwater mussel species (Bivalvia: Unionoida). J. Mollus. Stud. 73: 291-314., allow a more detailed evaluation of the distribution of the South American species of Hyriidae, Etheriidae and Mycetopodidae. Graf & Cummings (2007)GRAF, D.L. & CUMMINGS, K.S. 2007. Review of the systematic and global diversity of freshwater mussel species (Bivalvia: Unionoida). J. Mollus. Stud. 73: 291-314. divides the Neotropical region in six areas: Mesoamerica (including Cuba), Transandean (including the basins of rivers Magdalena and Maracaibo), Amazonas-Orinoco (including the Guyanas), Atlantic coastal streams (including the São Francisco River basin), Paraná-Paraguay and Patagonia. The two main families (Hyriidae and Mycetopodidae) are widespread in the region; Mycetopodidae occurs in all regions and Hyriidae in five of them (Figure 2). Etheriidae are limited to three regions. In the regions of Atlantic coastal streams, Paraná-Paraguay and Patagonia prevails species of Hyriidae; in the others regions, there are more Mycetopodidae species (Figure 2). The areas with the greatest total number of species are Amazonas-Orinoco (42 spp.) and Paraná-Paraguay (41 spp.), the first with the greatest number of Mycetopodidae (24 spp.) and the second with the greatest number of Hyriidae (21 spp.). Pereira et al. (2014)PEREIRA, D., MANSUR, M.C.D., DUARTE, L.D.S., OLIVEIRA, A.S., PIMPÃO, D.M., CALLIL, C.T., ITUARTE, C., PARADA, E., PEREDO, S., DARRIGRAN, G., SCARABINO, F., CLAVIJO, C., LARA, G., MIYAHIRA, I.C., RODRIGUEZ, M.T.R. & LASSO, C. 2014. Bivalve distribution in hydrographic regions in South America: historical overview and conservation. Hydrobiologia 735(1): 15-44. indicated the same areas as those of high diversity and pointed all region east of Andes (except by Northeast Brazil) as phylogenetically structured by Hyriidae and Mycetopodidae.

Figure 2
Number of species of Hyriidae and Mycetopodidae in different areas of Neotropical region. Based on the original data by Graf & Cummings (2007)GRAF, D.L. & CUMMINGS, K.S. 2007. Review of the systematic and global diversity of freshwater mussel species (Bivalvia: Unionoida). J. Mollus. Stud. 73: 291-314.. Key: Dark gray – Hyriidae; Black – Etheriidae and Light gray – Mycetopodidae.
Figure 4
Number of species of Rhipidodontini (Rhipidodonta + Diplodon) in Neotropical region. The regions that are not presented don´t have any Rhipidodontini species (i.e. Mesoamerica and Transandean). Based on the original data by Graf & Cummings (2007)GRAF, D.L. & CUMMINGS, K.S. 2007. Review of the systematic and global diversity of freshwater mussel species (Bivalvia: Unionoida). J. Mollus. Stud. 73: 291-314..

Comparing the representativeness of each family in different areas, we notice a trend towards a decrease in Mycetopodidae, along with an increase in Hyriidae (Figure 3), from North to South. The extremes are Mesoamerica, without Hyriidae species, and Patagonia where Hyriidae represents more than 70% of Unionida fauna. However, Patagonia is a poor region in mussels richness and this high percentage amounts to only three species. Etheriidae is always a small fraction of total species.

Figure 3
Representativeness of Hyriidae, Mycetopodidae and Etheriidae in the Neotropical region based on the original data by Graf & Cummings (2007)GRAF, D.L. & CUMMINGS, K.S. 2007. Review of the systematic and global diversity of freshwater mussel species (Bivalvia: Unionoida). J. Mollus. Stud. 73: 291-314.. Key: Dark gray – Hyriidae; Black – Etheriidae and Light gray – Mycetopodidae.

Figure 4 presents the diversity of Rhipidodontini (Rhipidodonta + Diplodon). There are no representatives of Rhipidodontini in the Mesoamerica and Transandean regions. The unique species of Hyriidae pointed out by Graf & Cummings (2007)GRAF, D.L. & CUMMINGS, K.S. 2007. Review of the systematic and global diversity of freshwater mussel species (Bivalvia: Unionoida). J. Mollus. Stud. 73: 291-314. to Transandean region is Castalia multisulcata Hupé, 1857 that belongs to Castaliini. Rhipidodontini represents most species of Hyriidae in Neotropics resulting in similarities between figure 4 and 2. The difference between the Amazonas-Orinoco region and Atlantic coastal streams region, lower in Figure 2 than in Figure 4, are due to the occurrence of exclusive Amazonian Hyriidae genera like Callonaia, Castaliella and Prisodon.Graf & Cummings (2007)GRAF, D.L. & CUMMINGS, K.S. 2007. Review of the systematic and global diversity of freshwater mussel species (Bivalvia: Unionoida). J. Mollus. Stud. 73: 291-314. included these genera in other tribes (Hyriini or Castaliini).

3. Taxonomy and systematics of Rhipidodontini

The most important studies concerning the systematics of Rhipidodontini (Figure 5) are shown in Table 2 and Appendix I (see Supplementary material): Simpson (1914)SIMPSON, C.T. 1914. A descriptive catalogue of the Naiades or pearly freshwater mussels. Privately published by Bryant Walker, Michigan., Ortmann (1921)ORTMANN, A.E. 1921. South American naiades, a contribution to the knowledge of the fresh-water mussels of South America. Mem. Carnegie Mus. 8(3): 451-670., Morretes (1949)MORRETES, F.L. 1949. Ensaio do catálogo dos moluscos do Brasil. Arq. mus. Paranaense 7: 5-216., Parodiz (1968)PARODIZ, J.J. 1968. Annotated catalogue of the genus Diplodon (Unionacea – Hyriidae). Sterkiana 30: 1-22., Haas (1969)HAAS, F. 1969. Superfamilia Unionacea. In Das Tierrich, Lieferung – vol 88 (Martens, R., Hennig W. & Wermuth, H., ed.). Walter de Gruyter and Co., Berlin., Simone (2006)SIMONE, L.R.L. 2006. Land and freshwater molluscs of Brazil. EGB, Fapesp, São Paulo. 390pp. and Graf & Cummings (2007)GRAF, D.L. & CUMMINGS, K.S. 2007. Review of the systematic and global diversity of freshwater mussel species (Bivalvia: Unionoida). J. Mollus. Stud. 73: 291-314.. The following discussion focused on specific epithet, regardless of the genus or subgenus the author employed. For example, Haas (1969)HAAS, F. 1969. Superfamilia Unionacea. In Das Tierrich, Lieferung – vol 88 (Martens, R., Hennig W. & Wermuth, H., ed.). Walter de Gruyter and Co., Berlin. used Diplodon (Rhipidodonta) rhombea Spix in Wagner, 1827, while Graf & Cummings (2007)GRAF, D.L. & CUMMINGS, K.S. 2007. Review of the systematic and global diversity of freshwater mussel species (Bivalvia: Unionoida). J. Mollus. Stud. 73: 291-314. used Rhipidodonta rhombea; regardless of genus designation, we regarded that both authors considered “rhombeus” as a valid species. Diplodon is traditionally divided in subgenera, mainly based on features of the shell, and the two most used are Rhipidodonta and Diplodon s.s..

Figure 5
Members of Rhipidodontini. A- Rhipidodonta charruana (d´Orbigny, 1835), MHNM (Museo Nacional de Historia Natural – Montivideo) 1210; B – Diplodon chilensis (Gray, 1828), LMD (Aquazoo Löbbecke Museum Düsseldorf) w/n (Lisikhe collection); C – Diplodon fontainianus (d´Orbigny, 1835), MHNM 6285; D – Diplodon parallelopipedon (Lea, 1834), LMD w/n (Lisikhe collection); E – Rhipidodonta hylaea (d´Orbigny, 1835), ZMB (Museum für Naturkunde) w/n (Paetel collection); F – Diplodon multistriatus (Lea, 1831), MHNM 3966; G – Diplodon parodizi Bonetto, 1962, MHNM – Soc. Taguató 670; H – Diplodon rhombeus Spix in Wagner, 1827, SMF (Senckenberg Forschungsinstitut und Naturmuseum)11248. Scale bar = 1cm.
Table 2
Number of species of Rhipidodontini considered valid by different authors. Noteworthy that for our purposes, a global scope work is almost equal to a South America scope because the recent fauna Rhipidodontini occurs only in South America. * - The author presents some Australian forms as Diplodon subgenera (Hyridella Swainson, 1840; Cucumaria Conrad, 1853; Laevirostris Simpson, 1900), that are not included in this table, in order to allow an equal comparison with other authors. ** - Considered doubtful by the author.

Simpson (1914)SIMPSON, C.T. 1914. A descriptive catalogue of the Naiades or pearly freshwater mussels. Privately published by Bryant Walker, Michigan. and Thiele (1934)THIELE, J. 1934. Handbuch der systematischen Weichtierkunde – part 3 (Scaphopoda/Bivalvia/Cephalopoda). 779-1022p. (in German, English translation by Bieler, R. & Mikkelsen, P.M. 1998. Handbook of systematic malacology – part 3 and 4. Smithsonian Institution Libraries, Washington D.C. p. 1193-1690). recognized three subgenera: Diplodon s.s., Rhipidodonta (= Cyclomya Simpson, 1900) and Bulloideus Simpson, 1900 (see Table 2 and Appendix I). Ortmann (1921)ORTMANN, A.E. 1921. South American naiades, a contribution to the knowledge of the fresh-water mussels of South America. Mem. Carnegie Mus. 8(3): 451-670. and Morretes (1949)MORRETES, F.L. 1949. Ensaio do catálogo dos moluscos do Brasil. Arq. mus. Paranaense 7: 5-216. recognized two subgenera, Diplodon and Rhipidodonta. The species placed in Bulloideus were usually included in Rhipidodonta by the authors that did not use the first subgenera. Haas (1969)HAAS, F. 1969. Superfamilia Unionacea. In Das Tierrich, Lieferung – vol 88 (Martens, R., Hennig W. & Wermuth, H., ed.). Walter de Gruyter and Co., Berlin. recognized four subgenera, adding Schleschiella Modell, 1950 to those mentioned previously. Ortmann (1921)ORTMANN, A.E. 1921. South American naiades, a contribution to the knowledge of the fresh-water mussels of South America. Mem. Carnegie Mus. 8(3): 451-670. was the first to notice differences in glochidium, however, he did not assign those variations to subgenera. The characteristics of glochidium were linked to subgenera by Bonetto (1961BONETTO, A.A. 1961. Investigaciones acerca de las formas larvales en el genero “Diplodon” y su aplicacion a los studios sistematicos. Direccion General de Recursos Naturales – Publicación Técnica, Santa Fé., 1965BONETTO, A.A. 1965. Las especies del genero Diplodon en el sistema hidrografico del rio de La Plata. In Anais do II Congresso Latino-Americano de Zoologia (Guimarães, L.R. coord.) Departamento de Zoologia da Secretária de Agricultura, São Paulo, p.37-54.) and Parodiz & Bonetto (1963)PARODIZ, J.J. & BONETTO, A.A. 1963. Taxonomy and Zoogeography relationships of the South American naiads (Pelecypoda: Unionacea and Mutelacea). Malacologia 1: 179-213.. Simone (2006)SIMONE, L.R.L. 2006. Land and freshwater molluscs of Brazil. EGB, Fapesp, São Paulo. 390pp. raised Rhipidodonta to genus status, an idea followed later by Graf & Cummings (2006GRAF, D.L. & CUMMINGS, K.S. 2006. Paleoheterodont diversity (Mollusca: Trigonoida + Unionoida): what we know and what we wish we knew about freshwater mussel evolution. Zool. J. Linnean Soc. 148: 343-394., 2007GRAF, D.L. & CUMMINGS, K.S. 2007. Review of the systematic and global diversity of freshwater mussel species (Bivalvia: Unionoida). J. Mollus. Stud. 73: 291-314.), considering Diplodon to encompass the species with parasite glochidium, and Rhipidodonta those with non-parasite glochidium. These two genera (Diplodon and Rhipidodonta) were included in tribe Rhipidodontini (Graf & Cummings 2007GRAF, D.L. & CUMMINGS, K.S. 2007. Review of the systematic and global diversity of freshwater mussel species (Bivalvia: Unionoida). J. Mollus. Stud. 73: 291-314.), with all species previously arranged in subgenera by other authors (Table 2, Appendix I). Simone (2006)SIMONE, L.R.L. 2006. Land and freshwater molluscs of Brazil. EGB, Fapesp, São Paulo. 390pp. do not presented an explanation to support his decision, and probably for this reason some authors like Pereira et al (2014)PEREIRA, D., MANSUR, M.C.D., DUARTE, L.D.S., OLIVEIRA, A.S., PIMPÃO, D.M., CALLIL, C.T., ITUARTE, C., PARADA, E., PEREDO, S., DARRIGRAN, G., SCARABINO, F., CLAVIJO, C., LARA, G., MIYAHIRA, I.C., RODRIGUEZ, M.T.R. & LASSO, C. 2014. Bivalve distribution in hydrographic regions in South America: historical overview and conservation. Hydrobiologia 735(1): 15-44. don´t followed his suggestions. It is clear that glochidium is a good diagnostic feature in Hyriidae (Parodiz & Boneto 1963, Mansur 1999MANSUR, M.C.D. 1999. Gloquídio de Diplodon martensi (Ihering) (Mollusca, Bivalvia, Hyriidae) e seu ciclo parasitário. Rev. Bras. Zool. 16(Supl. 2): 185-194., Mansur & Silva 1999MANSUR, M.C.D. & SILVA, M.G.O. 1999. Description of glochidia of five species of freshwater mussels (Hyriidae: Unionoidea) from South America. Malacologia 41(2): 475-483., Pimpão et al. 2012PIMPÃO, D.M., MANSUR, M.C.D., BERGONCI, P.E.A. & BEASLEY, C.R. 2012. Comparative morphometry and morphology of glochidial shells of Amazonian Hyriidae (Mollusca: Bivalvia: Unionoida). Am. Malacol. Bull. 30, 73–84.), but is also necessary to find other characteristics on the morphology of adult specimens as well as on molecular aspects to substantiate this division. It is also important to mention that in South America there are many under-sampled areas and undescribed glochidia of Rhipidodontini. We propose to adopted parsimoniously the suggestion of Simone (2006)SIMONE, L.R.L. 2006. Land and freshwater molluscs of Brazil. EGB, Fapesp, São Paulo. 390pp., using Rhipidodonta only to the species that the glochidium is described and without any doubts about identification.

Glochidium is known for 31 nominal species of Diplodon and for 17 nominal species of Rhipidodonta. In cases where the glochidium type is missing, the genus assignment is based only on adult shell morphology. That is the case of some species recognized in several works as Diplodon rhombeus (= Rhipidodonta rhombea after Simone 2006SIMONE, L.R.L. 2006. Land and freshwater molluscs of Brazil. EGB, Fapesp, São Paulo. 390pp.) (Figure 5G). There were also some cases of "change" of the glochidium type, after detailed revision; for example, glochidium type in Diplodon suavidicus (d´Orbigny, 1835) (Figure 5E) was firstly assigned as non-parasite (Simone 2006SIMONE, L.R.L. 2006. Land and freshwater molluscs of Brazil. EGB, Fapesp, São Paulo. 390pp.) and later as parasite (Pimpão et al. 2012PIMPÃO, D.M., MANSUR, M.C.D., BERGONCI, P.E.A. & BEASLEY, C.R. 2012. Comparative morphometry and morphology of glochidial shells of Amazonian Hyriidae (Mollusca: Bivalvia: Unionoida). Am. Malacol. Bull. 30, 73–84.). Pimpão et al. (2012)PIMPÃO, D.M., MANSUR, M.C.D., BERGONCI, P.E.A. & BEASLEY, C.R. 2012. Comparative morphometry and morphology of glochidial shells of Amazonian Hyriidae (Mollusca: Bivalvia: Unionoida). Am. Malacol. Bull. 30, 73–84. successfully used the glochidium to differentiate Amazonian species of Hyriidae, thus proving that glochidium can be powerful in species delimitation.

One concept that appeared in several older works was that of a “group of species” (Simpson 1914SIMPSON, C.T. 1914. A descriptive catalogue of the Naiades or pearly freshwater mussels. Privately published by Bryant Walker, Michigan., Ortmann 1921ORTMANN, A.E. 1921. South American naiades, a contribution to the knowledge of the fresh-water mussels of South America. Mem. Carnegie Mus. 8(3): 451-670., Haas 1930HAAS, F. 1930. Versuch einer kritischen Sichtung der sudamerikanischen Najaden, hauptsachlich an Hand der Sammlung des Senckenberg-Museums I. Senckenbergiana, 12: 175–195., 1931aHAAS, F. 1931a. Versuch einer kritischen Sichtung der sudamerikanischen Najaden, hauptsachlich an Hand der Sammlung des Senckenberg-Museums II. Senckenbergiana, 13: 30–52.,bHAAS, F. 1931b. Versuch einer kritischen Sichtung der sudamerikanischen Najaden, hauptsachlich an Hand der Sammlung des Senckenberg-Museums III. Senckenbergiana, 13: 87–110.), abandoned in more recent works (Haas 1969HAAS, F. 1969. Superfamilia Unionacea. In Das Tierrich, Lieferung – vol 88 (Martens, R., Hennig W. & Wermuth, H., ed.). Walter de Gruyter and Co., Berlin., Simone 2006SIMONE, L.R.L. 2006. Land and freshwater molluscs of Brazil. EGB, Fapesp, São Paulo. 390pp., Graf & Cummings 2007GRAF, D.L. & CUMMINGS, K.S. 2007. Review of the systematic and global diversity of freshwater mussel species (Bivalvia: Unionoida). J. Mollus. Stud. 73: 291-314.). A “group of species” includes several species that share some characteristics, usually the shell structure, and the most prominent species (according to the author) lend their name to the group. However, the characteristics of the different groups are not very clear, which led to some overlapping. A group of species does not hold taxonomic status and is used only as a way to organize the species by morphological similarity. All the authors that used “group of species” presented six groups; however, the choice of main species and the composition of each group was different (Table 3). The groups of Diplodon granosus (Bruguière, 1792) and D. delodontus (Lamarck, 1819) (= D. lacteolus) were mentioned by the three authors above (Simpson 1914SIMPSON, C.T. 1914. A descriptive catalogue of the Naiades or pearly freshwater mussels. Privately published by Bryant Walker, Michigan., Ortmann 1921ORTMANN, A.E. 1921. South American naiades, a contribution to the knowledge of the fresh-water mussels of South America. Mem. Carnegie Mus. 8(3): 451-670., Haas 1930HAAS, F. 1930. Versuch einer kritischen Sichtung der sudamerikanischen Najaden, hauptsachlich an Hand der Sammlung des Senckenberg-Museums I. Senckenbergiana, 12: 175–195., 1931aHAAS, F. 1931a. Versuch einer kritischen Sichtung der sudamerikanischen Najaden, hauptsachlich an Hand der Sammlung des Senckenberg-Museums II. Senckenbergiana, 13: 30–52.,bHAAS, F. 1931b. Versuch einer kritischen Sichtung der sudamerikanischen Najaden, hauptsachlich an Hand der Sammlung des Senckenberg-Museums III. Senckenbergiana, 13: 87–110.); however, the species included in each group were different according to each author. For example, Simpson (1914)SIMPSON, C.T. 1914. A descriptive catalogue of the Naiades or pearly freshwater mussels. Privately published by Bryant Walker, Michigan. allocated 27 species in the group of D. granosus, whereas Ortmann (1921)ORTMANN, A.E. 1921. South American naiades, a contribution to the knowledge of the fresh-water mussels of South America. Mem. Carnegie Mus. 8(3): 451-670. and Haas (1930HAAS, F. 1930. Versuch einer kritischen Sichtung der sudamerikanischen Najaden, hauptsachlich an Hand der Sammlung des Senckenberg-Museums I. Senckenbergiana, 12: 175–195., 1931aHAAS, F. 1931a. Versuch einer kritischen Sichtung der sudamerikanischen Najaden, hauptsachlich an Hand der Sammlung des Senckenberg-Museums II. Senckenbergiana, 13: 30–52.,bHAAS, F. 1931b. Versuch einer kritischen Sichtung der sudamerikanischen Najaden, hauptsachlich an Hand der Sammlung des Senckenberg-Museums III. Senckenbergiana, 13: 87–110.), proposed only one species with three subspecies. The concept of “group of species” was similar to the concept of “super-species” used by Parodiz (1968PARODIZ, J.J. 1968. Annotated catalogue of the genus Diplodon (Unionacea – Hyriidae). Sterkiana 30: 1-22., 1973PARODIZ, J.J. 1973. The species complex of Diplodon delodontus (Lamarck) (Unionacea – Hyriidae). Malacologia 14: 247-270.), but also not applied in subsequent works (e.g., Simone 2006SIMONE, L.R.L. 2006. Land and freshwater molluscs of Brazil. EGB, Fapesp, São Paulo. 390pp., Graf & Cummings 2006GRAF, D.L. & CUMMINGS, K.S. 2006. Paleoheterodont diversity (Mollusca: Trigonoida + Unionoida): what we know and what we wish we knew about freshwater mussel evolution. Zool. J. Linnean Soc. 148: 343-394.).

Table 3
Groups of species of Diplodon Spix in Wagner, 1827 presented by different authors.

Simpson (1914)SIMPSON, C.T. 1914. A descriptive catalogue of the Naiades or pearly freshwater mussels. Privately published by Bryant Walker, Michigan. presented the highest number of species (80), with seven new species and one new subspecies. Some species names were used only by Simpson (1914)SIMPSON, C.T. 1914. A descriptive catalogue of the Naiades or pearly freshwater mussels. Privately published by Bryant Walker, Michigan. like Diplodon ampullaceus (Lea, 1866), Diplodon aplatus (Reeve, 1865), Diplodon effulgens (Lea, 1856), Diplodon modestus (Küster, 1856), Diplodon quadrans (Lea, 1859) and Diplodon rufofuscus (Lea, 1859). Simpson (1914)SIMPSON, C.T. 1914. A descriptive catalogue of the Naiades or pearly freshwater mussels. Privately published by Bryant Walker, Michigan. also included some Australian species in Diplodon (subgenera: Hyridella, Cucumaria and Laevirostris), which were removed by subsequent authors (e.g.,Ortmann 1921ORTMANN, A.E. 1921. South American naiades, a contribution to the knowledge of the fresh-water mussels of South America. Mem. Carnegie Mus. 8(3): 451-670., Haas 1969HAAS, F. 1969. Superfamilia Unionacea. In Das Tierrich, Lieferung – vol 88 (Martens, R., Hennig W. & Wermuth, H., ed.). Walter de Gruyter and Co., Berlin.). Simpson (1914)SIMPSON, C.T. 1914. A descriptive catalogue of the Naiades or pearly freshwater mussels. Privately published by Bryant Walker, Michigan. synonymized some species names and described the species based mainly on their shell, using few information about the soft parts. Diplodon dunkerianus (Lea, 1856) and D. martensi (Ihering, 1893IHERING, H. 1893. Najaden von S. Paulo und die geographische verbreitung der süsswasserfauna von Südamerika. Arch. Naturgesch. 59: 45-140.) were only presented by Simpson (1914)SIMPSON, C.T. 1914. A descriptive catalogue of the Naiades or pearly freshwater mussels. Privately published by Bryant Walker, Michigan. and Parodiz (1968)PARODIZ, J.J. 1968. Annotated catalogue of the genus Diplodon (Unionacea – Hyriidae). Sterkiana 30: 1-22., among the authors of Table 2. However, there are more recent references to D. martensi (Mansur 1970MANSUR, M.C.D. 1970. Lista dos moluscos bivalves das famílias Hyriidae e Mycetopodidae para o estado do Rio Grande do Sul. Iheringia Ser. Zool. 39:33-95., Vaz et al. 1987VAZ J.F., MANTEGAZZA, E., TELES, H.M.S., LEITE S.P.S. & MORAIS, L.V.C. 1987. Levantamento planorbídico do Estado de São Paulo (Brasil): 4a Região Administrativa. Rev. Saúde Públ. S. Paulo 21: 371-379., Mansur 1999MANSUR, M.C.D. 1999. Gloquídio de Diplodon martensi (Ihering) (Mollusca, Bivalvia, Hyriidae) e seu ciclo parasitário. Rev. Bras. Zool. 16(Supl. 2): 185-194., Pfeifer & Pitoni 2003PFEIFER, N.T.S. & PITONI, V.L.L. 2003. Análise qualitativa estacional da fauna de moluscos límnicos no Delta do Jacuí, Rio Grande do Sul, Brasil. Biociências 11(2):145-158.) and D. dunkerianus (Amaral et al. 2008AMARAL, A.C.Z., RIBEIRO, C.V., MANSUR, M.C.D., SANTOS, S.B., AVELAR, W.E.P., MATTHEWS-CASCON, H., LEITE, F.P.P., MELO, G.A.S., COELHO, P.A., BUCKUP, G.B., BUCKUP, L., VENTURA, C.R.R. & TIAGO, C.G. 2008. A situação de ameaça dos invertebrados aquáticos no Brasil. In Livro vermelho da fauna brasileira ameaçada de extinção (Machado, A.B.M., Drummond, G.M. & Paglia, A.P., orgs). Ministério do Meio Ambiente, Brasilia, p. 156-301.).

Ortmann (1921)ORTMANN, A.E. 1921. South American naiades, a contribution to the knowledge of the fresh-water mussels of South America. Mem. Carnegie Mus. 8(3): 451-670. presented a similar number of species compared to later works (Haas 1969HAAS, F. 1969. Superfamilia Unionacea. In Das Tierrich, Lieferung – vol 88 (Martens, R., Hennig W. & Wermuth, H., ed.). Walter de Gruyter and Co., Berlin., Graf & Cummings 2007GRAF, D.L. & CUMMINGS, K.S. 2007. Review of the systematic and global diversity of freshwater mussel species (Bivalvia: Unionoida). J. Mollus. Stud. 73: 291-314.); however, the species listed were different. Ortmann based on the Unionida soft-parts morphology, proposed the first phylogenetic relationships of the Unionida families and subfamilies, as well as one of the first schemes to classify the South American naiades, which is still partially accepted. He also brought a wealth of information on the shell comparative morphology and glochidia of Hyriidae, a tool needed to better understand the high degree of polymorphism at the specific level.

The tendency to describe several new species decreases after Ortmann (1921)ORTMANN, A.E. 1921. South American naiades, a contribution to the knowledge of the fresh-water mussels of South America. Mem. Carnegie Mus. 8(3): 451-670.. However, Haas (1916HAAS, F. 1916. Nayades del viaje al Pacifico. Trabajos Mus. Nacion. Cienc. Nat., Madrid, (Zool.) 25:1-63., 1929HAAS, F. 1929. Beitrag zur Kenntnis der südamerikanischen Binnenmollusken. Senckenbergiana Biol. 11(:8-13., 1938HAAS, F. 1938. Neue Binnen-Mollusken aus Nordost-Brasilien. Arch. Moll. 70: 46-51., 1966HAAS, F. 1966. On some new non-marine mollusks from Colombia and Peru. Fieldiana Zool. 44(25):231-240.) still described four new species in separate works. This change in point of view is probably due to a better comprehension of shell polymorphism. The study of the naiads starts to acquire its current shape in Haas (1969)HAAS, F. 1969. Superfamilia Unionacea. In Das Tierrich, Lieferung – vol 88 (Martens, R., Hennig W. & Wermuth, H., ed.). Walter de Gruyter and Co., Berlin., when he upgraded and expanded the synonymic lists started by Simpson (1914)SIMPSON, C.T. 1914. A descriptive catalogue of the Naiades or pearly freshwater mussels. Privately published by Bryant Walker, Michigan. and Ortmann (1921)ORTMANN, A.E. 1921. South American naiades, a contribution to the knowledge of the fresh-water mussels of South America. Mem. Carnegie Mus. 8(3): 451-670.. Several species validated by Haas (1969)HAAS, F. 1969. Superfamilia Unionacea. In Das Tierrich, Lieferung – vol 88 (Martens, R., Hennig W. & Wermuth, H., ed.). Walter de Gruyter and Co., Berlin. remained with the same status in subsequent works. For example, out of the 27 species considered valid by Graf & Cummings (2007)GRAF, D.L. & CUMMINGS, K.S. 2007. Review of the systematic and global diversity of freshwater mussel species (Bivalvia: Unionoida). J. Mollus. Stud. 73: 291-314., 23 received the status of species or subspecies by Haas (1969)HAAS, F. 1969. Superfamilia Unionacea. In Das Tierrich, Lieferung – vol 88 (Martens, R., Hennig W. & Wermuth, H., ed.). Walter de Gruyter and Co., Berlin..

There are 149 species names associated to Diplodon and Rhipidodonta, excluding fossil species and nomen nudum (Parodiz 1968PARODIZ, J.J. 1968. Annotated catalogue of the genus Diplodon (Unionacea – Hyriidae). Sterkiana 30: 1-22., Bonetto & Tassara 1987BONETTO, A.A. & TASSARA, M.P. 1987. Contribucion al conocimento de dos nayades sudamericanas. Rev. Mus. Argent. Cienc. Nat. Bernardino Rivadavia Inst. Nac. Invest. Cienc. Nat – Zool. 24(11): 163-170.), 109 (73.15%) were used in species or subspecies rank by at least one of the authors of Table 2 and Appendix I (Simpson 1914SIMPSON, C.T. 1914. A descriptive catalogue of the Naiades or pearly freshwater mussels. Privately published by Bryant Walker, Michigan., Ortmann 1921ORTMANN, A.E. 1921. South American naiades, a contribution to the knowledge of the fresh-water mussels of South America. Mem. Carnegie Mus. 8(3): 451-670., Morretes 1949MORRETES, F.L. 1949. Ensaio do catálogo dos moluscos do Brasil. Arq. mus. Paranaense 7: 5-216., Parodiz 1968PARODIZ, J.J. 1968. Annotated catalogue of the genus Diplodon (Unionacea – Hyriidae). Sterkiana 30: 1-22., Haas 1969HAAS, F. 1969. Superfamilia Unionacea. In Das Tierrich, Lieferung – vol 88 (Martens, R., Hennig W. & Wermuth, H., ed.). Walter de Gruyter and Co., Berlin., Simone 2006SIMONE, L.R.L. 2006. Land and freshwater molluscs of Brazil. EGB, Fapesp, São Paulo. 390pp., Graf & Cummings 2007GRAF, D.L. & CUMMINGS, K.S. 2007. Review of the systematic and global diversity of freshwater mussel species (Bivalvia: Unionoida). J. Mollus. Stud. 73: 291-314.), leaving out 40 species names (26.85%) that were not used by any of them. Despite the high number of species names used (i.e. 109), most of them were used only by one or two authors, 28.86% and 18.80%, respectively (Figure 6, Appendix I).

Figure 6
Number of times that a determined nominal species is cited by the evaluated authors (Table 3). See the Appendix I to base data.

Only four species (2.68%) are recognized as valid by all authors, namely: Diplodon charruanus (d´Orbigny, 1835), Diplodon granosus, Diplodon hylaeus and Diplodon parallelopipedon (Lea, 1834) (Figure 5A,D,E). Besides these, all the authors cited the “set” ellipticus Spix in Wagner, 1827 + wagnerianus Simpson, 1900 that refers to the same biological species, though Haas (1969)HAAS, F. 1969. Superfamilia Unionacea. In Das Tierrich, Lieferung – vol 88 (Martens, R., Hennig W. & Wermuth, H., ed.). Walter de Gruyter and Co., Berlin. used ellipticus as a subspecies of Diplodon granosus. This agreement between the authors could suggest that these species are easily recognizable. This is (probably) true to Diplodon hylaeus and Diplodon parallelopipedon, which have peculiar shell characteristics. The others (charruanus/granosus/ellipticus) were among the first species described to South America and have priority but were involved in taxonomical problems.

Six names: D. besckeanus (Dunker, 1848), D. burroughianus (Lea, 1834), D. suavidicus (Lea, 1856), Diplodon gratus (Lea, 1860), Diplodon patagonicus (d’Orbigny, 1835) and Diplodon fontainianus (d´Orbigny, 1835) were used by six authors as species or subspecies, representing 4.03% of all names. Diplodon lacteolus is clearly a synonymy of Diplodon delodontus as already noted by Lea (1836)LEA, I. 1836. A synopsis of the family of naiades. Cary, Lea and Blanchard, Philadelphia. in the original description. The “set” lacteolus + delodontus was mentioned by all the authors except for Morretes (1949)MORRETES, F.L. 1949. Ensaio do catálogo dos moluscos do Brasil. Arq. mus. Paranaense 7: 5-216..

This evaluation illustrates the divergence among authors, a result of different characteristics employed for species differentiation. Even in the species recognized by most authors, there are considerable differences in descriptions and synonymic lists.

Despite the differences in the geographic scope of Simone (2006)SIMONE, L.R.L. 2006. Land and freshwater molluscs of Brazil. EGB, Fapesp, São Paulo. 390pp. and Graf & Cummings (2007)GRAF, D.L. & CUMMINGS, K.S. 2007. Review of the systematic and global diversity of freshwater mussel species (Bivalvia: Unionoida). J. Mollus. Stud. 73: 291-314., they agree completely about the eight species included in Rhipidodonta. The few differences between these authors comprised species included in Diplodon s.s. Five species in Graf & Cummings (2007)GRAF, D.L. & CUMMINGS, K.S. 2007. Review of the systematic and global diversity of freshwater mussel species (Bivalvia: Unionoida). J. Mollus. Stud. 73: 291-314. were not included in Simone (2006)SIMONE, L.R.L. 2006. Land and freshwater molluscs of Brazil. EGB, Fapesp, São Paulo. 390pp., namely: Diplodon chilensis (Gray, 1828); Diplodon flucki Morrison, 1943; Diplodon guaporensis Bonetto & Tassara, 1987; Diplodon losadae Haas, 1966 and Diplodon solidulus (Philippi, 1869). Despite the differences, Simone (2006)SIMONE, L.R.L. 2006. Land and freshwater molluscs of Brazil. EGB, Fapesp, São Paulo. 390pp. and Graf & Cummings (2007)GRAF, D.L. & CUMMINGS, K.S. 2007. Review of the systematic and global diversity of freshwater mussel species (Bivalvia: Unionoida). J. Mollus. Stud. 73: 291-314. were the most similar works presented in Appendix I.

4. Identification of Rhipidodontini

Shell characteristics were considered since the first researches on Rhipidodontini (e.g., Simpson 1914SIMPSON, C.T. 1914. A descriptive catalogue of the Naiades or pearly freshwater mussels. Privately published by Bryant Walker, Michigan.). The study of anatomical features was introduced by Ortmann (1921)ORTMANN, A.E. 1921. South American naiades, a contribution to the knowledge of the fresh-water mussels of South America. Mem. Carnegie Mus. 8(3): 451-670. and recently some molecular studies were done (e.g., Graf & Cummings 2006GRAF, D.L. & CUMMINGS, K.S. 2006. Paleoheterodont diversity (Mollusca: Trigonoida + Unionoida): what we know and what we wish we knew about freshwater mussel evolution. Zool. J. Linnean Soc. 148: 343-394., Santos-Neto 2016). However, none of these approaches have been exhausted.

The shell outline was used for a long time to differentiate the subgenera of Diplodon. For example, the rounded species were asserted to Rhipidodonta and the more elongated species to Diplodon s.s. This division based only on shell proven to be artificial and not agree with other aspects. Nowadays, the shell structures were still in use and were not described in detail for most species (Miyahira et al. 2013MIYAHIRA, I.C., MANSUR, M.C.D. & SANTOS, S.B. 2013. Revision of the type specimens of Diplodon ellipticus and Diplodon expansus. Spixiana 36: 173-182.). The most important characteristics of the shell are the umbo position, umbonal sculpture and hinge details. The ultra-structure of the shell was poorly studied in Hyriidae (Bieler et al. 2014BIELER, R., MIKKELSEN, P.M.; COLLINS, T.M., GLOVER, E.A., GONZÁLEZ, V.L., GRAF, D.L., HARPER, E.M., HEALY, J., KAWAUCHI, G.Y., SHARMA, P.P., STAUBACH, S., STRONG, E.E., TAYLOR, J.D., TËMKIN, I., ZARDUS, J.D., CLARK, S., GUZMÁN, A., McINTYRE, E., SHARP, P. & GIRIBET, G. 2014. Investigating the Bivalve Tree of Life – an exemplar-based approach combining molecular and novel morphological characters. Invertebrate Systematics 28: 32-115.) and must to be improved.

Only after the studies of Ortmann (1921)ORTMANN, A.E. 1921. South American naiades, a contribution to the knowledge of the fresh-water mussels of South America. Mem. Carnegie Mus. 8(3): 451-670. and Parodiz & Bonetto (1963)PARODIZ, J.J. & BONETTO, A.A. 1963. Taxonomy and Zoogeography relationships of the South American naiads (Pelecypoda: Unionacea and Mutelacea). Malacologia 1: 179-213. that provide the basic information on the glochidium type (with or without hooks) it was possible to link larva to subgenera and later to genera. Diplodon has glochidium with hooks and an obligate stage as parasite of fishes (Mansur et al. 2012MANSUR, M.C.D., SANTOS, C.P., PEREIRA, D., PAZ, I.C.P., ZURITA, M.L.L., RODRIGUEZ, M.T.R., NEHRKE, M.V. & BERGONCI, P.E.A. 2012. Moluscos límnicos invasores no Brasil: biologia, prevenção e controle. Redes Editora, Porto Alegre., Pimpão et al. 2012PIMPÃO, D.M., MANSUR, M.C.D., BERGONCI, P.E.A. & BEASLEY, C.R. 2012. Comparative morphometry and morphology of glochidial shells of Amazonian Hyriidae (Mollusca: Bivalvia: Unionoida). Am. Malacol. Bull. 30, 73–84.). The life cycle of D. martensi was described by Mansur (1999)MANSUR, M.C.D. 1999. Gloquídio de Diplodon martensi (Ihering) (Mollusca, Bivalvia, Hyriidae) e seu ciclo parasitário. Rev. Bras. Zool. 16(Supl. 2): 185-194. and remains as the unique species to have the cycle described in Brazil. The glochidium of Rhipidodonta is hookless and the life cycle still poorly known. The glochidium develop at the marsupium and the mussel release a juvenile (Wächtler et al. 2001WÄCHTLER, K., MANSUR, M.C.D., RICHTER, T. 2001. Larval type e early postlarval biology in Naiads (Unionoida). In Ecology e Evolution of the Freshwater Mussels Unionoida (Bauer G, Wächtler K., eds.). Springer-Verlag, Berlim. 93-125p., Mansur & Silva 1999MANSUR, M.C.D. & SILVA, M.G.O. 1999. Description of glochidia of five species of freshwater mussels (Hyriidae: Unionoidea) from South America. Malacologia 41(2): 475-483., Mansur et al. 2012MANSUR, M.C.D., SANTOS, C.P., PEREIRA, D., PAZ, I.C.P., ZURITA, M.L.L., RODRIGUEZ, M.T.R., NEHRKE, M.V. & BERGONCI, P.E.A. 2012. Moluscos límnicos invasores no Brasil: biologia, prevenção e controle. Redes Editora, Porto Alegre., Pimpão et al. 2012PIMPÃO, D.M., MANSUR, M.C.D., BERGONCI, P.E.A. & BEASLEY, C.R. 2012. Comparative morphometry and morphology of glochidial shells of Amazonian Hyriidae (Mollusca: Bivalvia: Unionoida). Am. Malacol. Bull. 30, 73–84.). Unfortunately the glochidium type was not described to all species of Rhipidodontini (Table 4). According to Pimpão et al. (2012)PIMPÃO, D.M., MANSUR, M.C.D., BERGONCI, P.E.A. & BEASLEY, C.R. 2012. Comparative morphometry and morphology of glochidial shells of Amazonian Hyriidae (Mollusca: Bivalvia: Unionoida). Am. Malacol. Bull. 30, 73–84. the glochidium was useful not only to separate the genera but also to identify species based on morphometrics and a detailed description. In order to avoid unnecessary taxonomical fluctuations, it is recommended that species remains at Diplodon until information on glochidia were obtained.

Table 4
Nominal species of Rhipidodontini with glochidium type described in the literature. (Lea 1869, Ortmann 1921ORTMANN, A.E. 1921. South American naiades, a contribution to the knowledge of the fresh-water mussels of South America. Mem. Carnegie Mus. 8(3): 451-670., Bonetto 1954BONETTO, A.A. 1954. Nayades del rio Parana – el genero Diplodon en el biotope isleño del Parana medio e inferior. Secretaria de Agricultura, Ganaderia e Industrias – Publicación Tecnica, Santa Fé., 1960, 1961, Bonetto & Ezcurra-de-Drago 1965, Alvarenga & Ricci 1979, Bonetto et al. 1986BONETTO, A.A., TASSARA, M.P. & RUMI, A. 1986. Australis n. subgen. de Diplodon Spix (Bivalvia, Unionacea) y posibles relaciones con Hyriidae australianos. Bol. Soc. Biol. Concepc. 57: 55-61., Mansur & Campos-Velho 1990MANSUR, M.C.D. & CAMPOS-VELHO, N.M.R. 1990. Técnicas para o estudo dos gloquídios de Hyriidae (Mollusca, Bivalvia, Unionoida). Acta Biol. Leopold. 12(1): 5-18., Ricci et. al. 1990RICCI, C.N., ALVARENGA, L.C.F. & COELHO, A.C.S. 1990. Gloquídios de Diplodon Spix, 1827: D. (D.) multistriatus (Lea, 1831) (Mollusca, Bivalvia, Hyriidae). Bol. Mus. Nac. Zool. 344: 1-10., Martinez-Escabassiere & Royero 1995, Mansur & Silva 1999MANSUR, M.C.D. & SILVA, M.G.O. 1999. Description of glochidia of five species of freshwater mussels (Hyriidae: Unionoidea) from South America. Malacologia 41(2): 475-483., Pimpão et al. 2012PIMPÃO, D.M., MANSUR, M.C.D., BERGONCI, P.E.A. & BEASLEY, C.R. 2012. Comparative morphometry and morphology of glochidial shells of Amazonian Hyriidae (Mollusca: Bivalvia: Unionoida). Am. Malacol. Bull. 30, 73–84.). We used Diplodon for all species to avoid new combinations without further studies

Some details of internal morphology was described only to the following species, Diplodon charruanus, D. pilsbry Marshall, 1928, D. besckeanus, D. multistriatus (Lea, 1831), D. rhombeus fontainianus and D. rotundus gratus (Hebling & Penteado 1974HEBLING, N.J. & PENTEADO, A.M.G. 1974. Anatomia functional de Diplodon rotundus gratus Wagner, 1827 (Mollusca, Bivalvia). Rev. Bras. Biol. 34(1): 67-80., Alvarenga & Ricci 1981ALVARENGA, L.C.F. & RICCI, C. 1981. Morfologia das partes moles de Diplodon (D.) besckeanus (Dunker, 1849) (Bivalvia, Unionoidea, Hyriidae). Bol. Mus. Nac., Zool. 298: 1-8., Mansur & Anflor 1982MANSUR, M.C.D. & ANFLOR, L.M. 1982. Diferenças morfológicas entre Diplodon charruanus (Orbigny, 1835) e D. pilsbry Marshall, 1928 (Bivalvia: Hyriidae). Iheringia Ser. Zool.60: 101-106., Ricci et at 1988, Avelar & Cunha 2009AVELAR, W.E.P. & CUNHA, A.D. 2009. The anatomy and functional morphology of Diplodon rhombeus fontainianus (Orbigny, 1835) (Mollusca, Bivalvia, Hyriidae). Braz. J. Biol. 69(4):1153-1163.). Meyer et al. (2012MEYER, A.A.N., MARTIN, J.K. & OLIVEIRA, E. 2013. Ocorrência e caracterização histológica de marsúpios de Diplodon expansus (Küster, 1856) (Mollusca, Bivalve, Hyriidae) no rio Piraquara, Paraná, Brasil. Biotemas 26(1): 97-108., 2014MEYER, A.A.N., OLIVEIRA, E., TEIXEIRA, T.B. & VIESSER, J.A. 2014. Classes de comprimento e descrição histológica das gônadas de Diplodon ellipticus (Wagner, 1827) (Mollusca, Bivalvia, Hyriidae) em um lago artificial, Morretes, Paraná, Brasil. Biotemas 27(3): 81-96.) described the reproductive system of D. expansus (Küster, 1856) and D. ellipticus from a histological perspective. Considering the reduced knowledge about Rhipidodontini morphology it is difficult to elect good diagnostic features in soft parts. Until now some differences between species were found with success on the outline and morphology of branchiae, position of marsupium, labial palps and stomach.

Only four species of Diplodon were used in molecular approaches: D. deceptus Simpson, 1914, D. suavidicus, D. demeraraensis (Lea, 1859) and D. chilensis (Hoeh & Bogan 2000HOEH, W.R. & BOGAN, A.E. 2000. On becoming cemented: evolutionary relationships among the genera in freshwater bivalve family Etheriidae (Bivalvia: Unionoida). In: Harper, E.M., Taylor, J.D. Cramer, J.A. (eds) The evolutionary biology of the Bivalvia. Geological Society, London. p. 159-168., Graf et al. 2015GRAF, D.L., JONES, H., GENEVA, A.J.; PFEIFER III, J.M. & KLUNZINGER, M.W. 2015. Molecular phylogenetics analysis supports a Gondwanan origin of the Hyriidae (Mollusca: Bivalvia: Unionoida) and the paraphyly of Australasian taxa. Mol. Phylogenet. Evol. 85: 1-9., Santos-Neto et al. 2016SANTOS-NETO, G.C., BEASLEY, C.R., SCHNEIDER, H., PIMPÃO, D.M., HOEH, W.R., SIMONE, L.R.L. & TAGLIARO, C.H. 2016. Genetic relationships among freshwater mussel species from fifteen Amazonian rivers and inferences on the evolution of the Hyriidae (Mollusca: Bivalvia: Unionoida). Mol. Phylogenet. Evol. 100: 148-159.). All these molecular studies deals with wider questions, inner relations of Rhipidodontini were never investigated in detail.

Analyzing all these information, it is clear that several gaps remain in available knowledge about Rhipidodontini. More data are necessary to provide better species identification and consequently the genera differentiation. Nowadays, the unique secure attribute to separate Diplodon and Rhipidodonta is the glochidium type. All these data will be necessary to discover the internal relationships of Rhipidodontini.

5. Ecological preferences of Rhipidodontini

The species can occur in lentic or lotic habitats, from small streams to big rivers and lakes; however, they are not common in strong currents. They tolerate a wide granulometric range, but prefer fine sediments, usually rich in organic matter. Some species can occur between or below pebbles, or even in rock cracks. They usually start appearing at a depth of 30 cm. They are sometimes found associated to roots of aquatic plants (Avelar & Cunha 2009AVELAR, W.E.P. & CUNHA, A.D. 2009. The anatomy and functional morphology of Diplodon rhombeus fontainianus (Orbigny, 1835) (Mollusca, Bivalvia, Hyriidae). Braz. J. Biol. 69(4):1153-1163.). They prefer the final sections of the river, due to the highest amount of nutrients, and are rare or absent in headwaters (Pereira et al. 2011PEREIRA, D., ARRUDA, J.O., MENEGAT, R., PORTO, M.L., SCHWARZBOLD, A. & HARTZ, S.M. 2011. Guildas tróficas, composição e distribuição de espécies de moluscos límnicos no gradiente fluvial de um riacho subtropical brasileiro. Biotemas 24(1): 21-36., Miyahira et al. 2017MIYAHIRA, I.C., CARNEIRO, J.B., GONÇALVES, I.C.B., LACERDA, L.E.M., OLIVEIRA, J.L., VASCONCELLOS, M.C. & SANTOS, S.B. 2017. Freshwater mollusks and environmental assessment of Guandu River, Rio de Janeiro, Brazil. Biota Neotropica 17(3): http://dx.doi.org/10.1590/1676-0611-BN-2017-0342.
http://dx.doi.org/10.1590/1676-0611-BN-2...
). They can share space with other native freshwater mussels, as is commonly seen in southern Brazil, northern Argentina and Uruguay, apparently without harm to the species (Mansur & Pereira 2006MANSUR, M.C.D. & PEREIRA, D. 2006. Bivalves límnicos da bacia do rio dos Sinos, Rio Grande do Sul, Brasil (Bivalvia, Unionoida, Veneroida e Mytiloida). Rev. Bras. Zool. 23(4): 1123-1147., Pereira et al. 2011PEREIRA, D., ARRUDA, J.O., MENEGAT, R., PORTO, M.L., SCHWARZBOLD, A. & HARTZ, S.M. 2011. Guildas tróficas, composição e distribuição de espécies de moluscos límnicos no gradiente fluvial de um riacho subtropical brasileiro. Biotemas 24(1): 21-36., 2014PEREIRA, D., MANSUR, M.C.D., DUARTE, L.D.S., OLIVEIRA, A.S., PIMPÃO, D.M., CALLIL, C.T., ITUARTE, C., PARADA, E., PEREDO, S., DARRIGRAN, G., SCARABINO, F., CLAVIJO, C., LARA, G., MIYAHIRA, I.C., RODRIGUEZ, M.T.R. & LASSO, C. 2014. Bivalve distribution in hydrographic regions in South America: historical overview and conservation. Hydrobiologia 735(1): 15-44., Mansur et al. 2012MANSUR, M.C.D., SANTOS, C.P., PEREIRA, D., PAZ, I.C.P., ZURITA, M.L.L., RODRIGUEZ, M.T.R., NEHRKE, M.V. & BERGONCI, P.E.A. 2012. Moluscos límnicos invasores no Brasil: biologia, prevenção e controle. Redes Editora, Porto Alegre.). The species of Rhipidodontini are sensitive to environmental changes and suffer with domestic and industrial sewage discharge, the main cause of decrease in populations of freshwater mussels (Strayer et al. 2004STRAYER, D.L., DOWINING, J.A., HAAG, W.R., KING, T.L., LAYZER, J.B., NEWTON, T.J. & NICHOLS, S.J. 2004. Changing perspectives on pearly mussels, North America’s most imperiled animals. Bioscience 54(5): 429-439.; Miyahira et al. 2012MIYAHIRA, I.C., SANTOS, S.B., MANSUR, M.C.D. & CARNEIRO, J.B. 2012. Freshwater mussels in Brazil: past, present and future, at least, we hope they have one. American Conchologist 40: 16-18.; Mansur et al. 2012MANSUR, M.C.D., SANTOS, C.P., PEREIRA, D., PAZ, I.C.P., ZURITA, M.L.L., RODRIGUEZ, M.T.R., NEHRKE, M.V. & BERGONCI, P.E.A. 2012. Moluscos límnicos invasores no Brasil: biologia, prevenção e controle. Redes Editora, Porto Alegre.; Pereira et al. 2014PEREIRA, D., MANSUR, M.C.D., DUARTE, L.D.S., OLIVEIRA, A.S., PIMPÃO, D.M., CALLIL, C.T., ITUARTE, C., PARADA, E., PEREDO, S., DARRIGRAN, G., SCARABINO, F., CLAVIJO, C., LARA, G., MIYAHIRA, I.C., RODRIGUEZ, M.T.R. & LASSO, C. 2014. Bivalve distribution in hydrographic regions in South America: historical overview and conservation. Hydrobiologia 735(1): 15-44.).

6. Threats and the conservation of Unionida

Freshwater mussels are among the most endangered species (Strayer et al. 2004STRAYER, D.L., DOWINING, J.A., HAAG, W.R., KING, T.L., LAYZER, J.B., NEWTON, T.J. & NICHOLS, S.J. 2004. Changing perspectives on pearly mussels, North America’s most imperiled animals. Bioscience 54(5): 429-439., Bogan 2008BOGAN, A.E. 2008. Global diversity of freshwater mussels (Mollusca, Bivalvia) in freshwater. Hydrobiologia 595: 139-147., Santos et al. 2009SANTOS, S.B., PIMENTA, A.D., THIENGO, S.C., THOMÉ, J.W., ABSALÃO, R.S., MANSUR, M.C.D., VIDIGAL, T.H.D., FERNANDEZ, M.A., TOMÁS, A.R.G., MESQUITA, E.F.M., SALGADO, N.C., MATTHEWS-CASCON, H., MARTINS, I.X., ROCHA-BARREIRA, C. & KAWANO, T. 2009. Mollusca. In Estado da arte e perspectivas para a Zoologia no Brasil (Rocha, R.M. & Boeger, W.A.P., orgs.) Editora UFPR, Curitiba. p.65-90., Miyahira et al. 2012MIYAHIRA, I.C., SANTOS, S.B., MANSUR, M.C.D. & CARNEIRO, J.B. 2012. Freshwater mussels in Brazil: past, present and future, at least, we hope they have one. American Conchologist 40: 16-18.). The main cause of this threat is the habitat change. At the basin of the Paraná River, one of the richest areas in Brazil regarding freshwater mussels, there is a series of 70 reservoirs, turning a long-term survival difficult for mussels (Santos et al. 2009SANTOS, S.B., PIMENTA, A.D., THIENGO, S.C., THOMÉ, J.W., ABSALÃO, R.S., MANSUR, M.C.D., VIDIGAL, T.H.D., FERNANDEZ, M.A., TOMÁS, A.R.G., MESQUITA, E.F.M., SALGADO, N.C., MATTHEWS-CASCON, H., MARTINS, I.X., ROCHA-BARREIRA, C. & KAWANO, T. 2009. Mollusca. In Estado da arte e perspectivas para a Zoologia no Brasil (Rocha, R.M. & Boeger, W.A.P., orgs.) Editora UFPR, Curitiba. p.65-90., Mansur et al. 2012MANSUR, M.C.D., SANTOS, C.P., PEREIRA, D., PAZ, I.C.P., ZURITA, M.L.L., RODRIGUEZ, M.T.R., NEHRKE, M.V. & BERGONCI, P.E.A. 2012. Moluscos límnicos invasores no Brasil: biologia, prevenção e controle. Redes Editora, Porto Alegre., Pereira et al. 2014PEREIRA, D., MANSUR, M.C.D., DUARTE, L.D.S., OLIVEIRA, A.S., PIMPÃO, D.M., CALLIL, C.T., ITUARTE, C., PARADA, E., PEREDO, S., DARRIGRAN, G., SCARABINO, F., CLAVIJO, C., LARA, G., MIYAHIRA, I.C., RODRIGUEZ, M.T.R. & LASSO, C. 2014. Bivalve distribution in hydrographic regions in South America: historical overview and conservation. Hydrobiologia 735(1): 15-44.). The change of lotic to lentic habitats caused by the dams profoundly changes the physical and chemical conditions, affecting not only the mussels but also the host fishes (in the case of parasitic life cycle of Diplodon). This situation creates relictual populations of mussels, alive but fated to die, because they cannot reproduce or disperse without fish host. The long life achieved by these mussels allows them to have a long survival, but without any hope (Philipp & Abele, 2009PHILIPP, E.E.R. & ABELE, D. 2009. Masters of longevity: lessons from long-lived bivalves – A mini review. Gerontology: 1-11.). This situation created an extinction debt that already stated to be paid in North American fauna with several recent extinctions (Haag 2012HAAG, W.R. 2012. North American freshwater mussels: natural history, ecology and conservation. Cambridge University Press, Cambridge.).

Freshwater mussels were exploited by the mother of pearl button industry for a long time, mainly in North America (Neves 1999NEVES, R.J. 1999. Conservation and commerce: management of freshwater mussel (Bivalvia: Unionoidea) resources in the United States. Malacologia 41(2): 461-474., Haag 2012HAAG, W.R. 2012. North American freshwater mussels: natural history, ecology and conservation. Cambridge University Press, Cambridge.), but also in South America (Beasley 2001BEASLEY, C.R. 2001. The impact of explotation on freshwater mussels (Bivalvia: Hyriidae) in the Tocantins river, Brazil. Stud. Neotrop. Fauna 36(2): 159-165., Matos 2007MATOS, E. 2007. Ação parasitária em cultivo de moluscos bivalves: um estudo de casa no Nordeste do estado do Pará. In Tópicos em Malacologia – Ecos do XVIII Encontro Brasileiro de Malacologia (Santos, S.B., Pimenta, A.D., Thiengo, S.C., Fernandez, M.A. & Absalão, R.S., orgs.). Technical Books, Rio de Janeiro, p.209-216., Clavijo 2017CLAVIJO, C. 2017. The Pearl industry and pioneering research in biology and conservation of pearl mussels (Unionoida) in the Río de La Plata Basin. Tentacle 25: 14-15.). That exploitation caused the decline of several mussel populations in the USA, especially in the first half of the twenty century (Strayer et al. 2004STRAYER, D.L., DOWINING, J.A., HAAG, W.R., KING, T.L., LAYZER, J.B., NEWTON, T.J. & NICHOLS, S.J. 2004. Changing perspectives on pearly mussels, North America’s most imperiled animals. Bioscience 54(5): 429-439., Haag 2012HAAG, W.R. 2012. North American freshwater mussels: natural history, ecology and conservation. Cambridge University Press, Cambridge.). Although usually considered a threat from the olden days, populations of Paxyodon, Triplodon and Castalia in the Brazilian Amazon are still exploited by the button industry (Beasley 2001BEASLEY, C.R. 2001. The impact of explotation on freshwater mussels (Bivalvia: Hyriidae) in the Tocantins river, Brazil. Stud. Neotrop. Fauna 36(2): 159-165., Matos 2007MATOS, E. 2007. Ação parasitária em cultivo de moluscos bivalves: um estudo de casa no Nordeste do estado do Pará. In Tópicos em Malacologia – Ecos do XVIII Encontro Brasileiro de Malacologia (Santos, S.B., Pimenta, A.D., Thiengo, S.C., Fernandez, M.A. & Absalão, R.S., orgs.). Technical Books, Rio de Janeiro, p.209-216.).

Recently, one of the major threats to the native bivalves is the introduction of invasive species (Haag 2012HAAG, W.R. 2012. North American freshwater mussels: natural history, ecology and conservation. Cambridge University Press, Cambridge., Mansur et al. 2012MANSUR, M.C.D., SANTOS, C.P., PEREIRA, D., PAZ, I.C.P., ZURITA, M.L.L., RODRIGUEZ, M.T.R., NEHRKE, M.V. & BERGONCI, P.E.A. 2012. Moluscos límnicos invasores no Brasil: biologia, prevenção e controle. Redes Editora, Porto Alegre.). Among the most harmful species that were introduced to Brazil are Limnoperna fortunei, Corbicula fluminea (Müller, 1774), Corbicula fluminalis (Müller, 1774) and Corbicula largillierti (Philippi, 1844). Limnoperna fortunei (golden mussel) has caused the worst damages to native mussels populations, as they grow over any hard substrate, including the shell of native mussels, preventing them to open their valves, causing death by suffocation and starvation (Mansur et al. 2004aMANSUR, M.C.D., QUEVEDO, C.B., SANTOS, C.P. & CALLIL, C.T. 2004a. Provavéis vias de introdução de Limnoperna fortunei (Dunker, 1857) (Mollusca, Bivalvia, Mytilidae) na bacia da Laguna dos Patos, Rio Grande do Sul e novos registros de invasão no Brasil pelas bacias do Paraná e Paraguai. In Água de lastro e bioinvasão (Silva, J.S.V. & Souza, R.C.C.L, orgs) Editora Interciência, Rio de Janeiro, p. 33-38., Darrigran & Damborenea 2006DARRIGRAN, G. & DAMBORENEA, C. 2006. Bio-invasión del mejillón dorado en el continente americano. Editorial de la Universidad de La Plata. La Plata, La Plata., Mansur et al. 2012MANSUR, M.C.D., SANTOS, C.P., PEREIRA, D., PAZ, I.C.P., ZURITA, M.L.L., RODRIGUEZ, M.T.R., NEHRKE, M.V. & BERGONCI, P.E.A. 2012. Moluscos límnicos invasores no Brasil: biologia, prevenção e controle. Redes Editora, Porto Alegre.). Besides the ecological problems, the introduced species can cause several economic losses to industries and energy plants; clogging pipes, filters and other structures (Mansur et al. 2004aMANSUR, M.C.D., QUEVEDO, C.B., SANTOS, C.P. & CALLIL, C.T. 2004a. Provavéis vias de introdução de Limnoperna fortunei (Dunker, 1857) (Mollusca, Bivalvia, Mytilidae) na bacia da Laguna dos Patos, Rio Grande do Sul e novos registros de invasão no Brasil pelas bacias do Paraná e Paraguai. In Água de lastro e bioinvasão (Silva, J.S.V. & Souza, R.C.C.L, orgs) Editora Interciência, Rio de Janeiro, p. 33-38.,bMANSUR, M.C.D., CALLIL, C.T., CARDOSO, F.R. & IBARRA, J.A.A. 2004b. Uma retrospectiva e mapeamento da invasão de espécies de Corbicula (Mollusca, Bivalvia, Veneroida, Corbiculidae) oriundas do sudeste Asiático, na América do Sul. In Água de lastro e bioinvasão (Silva, J.S.V. & Souza, R.C.C.L, orgs) Editora Interciência, Rio de Janeiro, p.39-58., Darrigran & Damborenea 2006DARRIGRAN, G. & DAMBORENEA, C. 2006. Bio-invasión del mejillón dorado en el continente americano. Editorial de la Universidad de La Plata. La Plata, La Plata., Mansur 2007MANSUR, M.C.D. 2007. Moluscos da classe Bivalvia que tiveram sucesso ao se irradiarem no ambiente de água doce. 27-29p. In: Livro de Resumos do XX Encontro Brasileiro de Malacologia, Rio de Janeiro. 406pp., Darrigran et al. 2007DARRIGRAN, G., DAMBORENEA, C. & GRECO, N. 2007. Freshwater invasive bivalves in man-made environments: A case study of larvae biology of Limnoperna fortunei in a Hydroelectric Power Plant in South America. AMBIO, 36(7):575-579). The damages caused by these bivalves were recently reviewed by Boltovskoy & Correa (2015)BOLTOVSKOY, D. & CORREA, N. 2015. Ecosystem impacts of the invasive bivalve Limnoperna fortunei (golden mussel) in South America. Hydrobiologia 746: 81-95..

In the 2008 edition of the Brazilian Red Book of Threatened Species, 26 out of the 29 listed molluscs are freshwater mussels, including ten species of Diplodon (Amaral et al. 2008AMARAL, A.C.Z., RIBEIRO, C.V., MANSUR, M.C.D., SANTOS, S.B., AVELAR, W.E.P., MATTHEWS-CASCON, H., LEITE, F.P.P., MELO, G.A.S., COELHO, P.A., BUCKUP, G.B., BUCKUP, L., VENTURA, C.R.R. & TIAGO, C.G. 2008. A situação de ameaça dos invertebrados aquáticos no Brasil. In Livro vermelho da fauna brasileira ameaçada de extinção (Machado, A.B.M., Drummond, G.M. & Paglia, A.P., orgs). Ministério do Meio Ambiente, Brasilia, p. 156-301.). However, a recent re-evaluation of the list (Santos et al. 2015SANTOS, S.B., MIYAHIRA, I.C., SALGADO, N.C., HEYDRICH, I., PENA, M.S., COLLEY, E., FERNANDEZ, M.A., THIENGO, S.C., GOMES, S.R., SILVA, M.J.M., GONÇALVES, I.C.B., LACERDA, L.E.M., TALLARICO, L.F. & MARTINS, D.S. 2015. Observations on review of the list of endangered continental molluscs of Brazil. Tentacle 23: 26-28.), which strictly used the criteria of IUCN listed only two species as threatened, 11 as Data Deficient and 9 as Near Threatened. It is clear that the environmental conditions in Brazil not improved in these few years. This is actually an evidence of the lack of data and the risk of extinction must be re-evaluated considering the Brazilian reality. The threat to freshwater mussels is a global phenomenon. In North America, there are 73 species critically endangered and 37 probably extinct (Neves 1999NEVES, R.J. 1999. Conservation and commerce: management of freshwater mussel (Bivalvia: Unionoidea) resources in the United States. Malacologia 41(2): 461-474., Strayer et al. 2004STRAYER, D.L., DOWINING, J.A., HAAG, W.R., KING, T.L., LAYZER, J.B., NEWTON, T.J. & NICHOLS, S.J. 2004. Changing perspectives on pearly mussels, North America’s most imperiled animals. Bioscience 54(5): 429-439., Haag 2012HAAG, W.R. 2012. North American freshwater mussels: natural history, ecology and conservation. Cambridge University Press, Cambridge.).

Knowledge on freshwater mussels of Brazil is not sufficient, with several important data to species extinction evaluation risk missing, such as information about population dynamics and reproductive cycle. This prevents the inclusion of species in IUCN risk categories, unless if distribution evidence is used, the better data that we have. However, even the information about distribution has problems. Many times the distribution of freshwater mussels is assigned to a hydrographic basin as a whole (e.g.,Simone 2006SIMONE, L.R.L. 2006. Land and freshwater molluscs of Brazil. EGB, Fapesp, São Paulo. 390pp., Mansur et al. 2012MANSUR, M.C.D., SANTOS, C.P., PEREIRA, D., PAZ, I.C.P., ZURITA, M.L.L., RODRIGUEZ, M.T.R., NEHRKE, M.V. & BERGONCI, P.E.A. 2012. Moluscos límnicos invasores no Brasil: biologia, prevenção e controle. Redes Editora, Porto Alegre.); however, the situation in the “real world” is quite different, as the distribution of the species is not homogeneous and depends on several environmental factors (Haag 2012HAAG, W.R. 2012. North American freshwater mussels: natural history, ecology and conservation. Cambridge University Press, Cambridge., Mansur et al. 2012MANSUR, M.C.D., SANTOS, C.P., PEREIRA, D., PAZ, I.C.P., ZURITA, M.L.L., RODRIGUEZ, M.T.R., NEHRKE, M.V. & BERGONCI, P.E.A. 2012. Moluscos límnicos invasores no Brasil: biologia, prevenção e controle. Redes Editora, Porto Alegre.). The mussels assemblages are patchily distributed and the movements in adult mussels are restricted (Pereira et al 2011PEREIRA, D., ARRUDA, J.O., MENEGAT, R., PORTO, M.L., SCHWARZBOLD, A. & HARTZ, S.M. 2011. Guildas tróficas, composição e distribuição de espécies de moluscos límnicos no gradiente fluvial de um riacho subtropical brasileiro. Biotemas 24(1): 21-36., Haag 2012HAAG, W.R. 2012. North American freshwater mussels: natural history, ecology and conservation. Cambridge University Press, Cambridge., Vaughn 2017VAUGHN, C.C. 2017. Ecosystem services provided by freshwater mussels. Hydrobiologia. DOI 10.1007/s10750-017-3139-x
https://doi.org/10.1007/s10750-017-3139-...
, Miyahira et al. 2017MIYAHIRA, I.C., CARNEIRO, J.B., GONÇALVES, I.C.B., LACERDA, L.E.M., OLIVEIRA, J.L., VASCONCELLOS, M.C. & SANTOS, S.B. 2017. Freshwater mollusks and environmental assessment of Guandu River, Rio de Janeiro, Brazil. Biota Neotropica 17(3): http://dx.doi.org/10.1590/1676-0611-BN-2017-0342.
http://dx.doi.org/10.1590/1676-0611-BN-2...
). Thus, the distribution of a mussel can never consider the basin as the whole for evaluation of extinction risks. Pereira et al. 2011 evaluated six sites along a gradient at a stream in the state of Rio Grande do Sul (Brazil); Anodontites trapesialis (Lamarck, 1819) and Anodontites lucidus (d’Orbigny, 1835) were found in one site; A. patagonicus (Lamarck, 1919) in two; and Diplodon pilsbry in three. Similar situation is found by Miyahira et al. (2017)MIYAHIRA, I.C., CARNEIRO, J.B., GONÇALVES, I.C.B., LACERDA, L.E.M., OLIVEIRA, J.L., VASCONCELLOS, M.C. & SANTOS, S.B. 2017. Freshwater mollusks and environmental assessment of Guandu River, Rio de Janeiro, Brazil. Biota Neotropica 17(3): http://dx.doi.org/10.1590/1676-0611-BN-2017-0342.
http://dx.doi.org/10.1590/1676-0611-BN-2...
in a river at state of Rio de Janeiro (Brazil); A. trapesialis and D. ellipticus where found respectively in two and three sites out of ten surveyed. Another problem about distribution information is the use of old data obtained in literature and museums records (e.g.,Mansur & Pereira 2006MANSUR, M.C.D. & PEREIRA, D. 2006. Bivalves límnicos da bacia do rio dos Sinos, Rio Grande do Sul, Brasil (Bivalvia, Unionoida, Veneroida e Mytiloida). Rev. Bras. Zool. 23(4): 1123-1147., Simone 2006SIMONE, L.R.L. 2006. Land and freshwater molluscs of Brazil. EGB, Fapesp, São Paulo. 390pp., Miyahira et al. 2013MIYAHIRA, I.C., MANSUR, M.C.D. & SANTOS, S.B. 2013. Revision of the type specimens of Diplodon ellipticus and Diplodon expansus. Spixiana 36: 173-182.). Thus, the distribution presented in most works is closest to the original, but also includes several places where species do not occur anymore, leading to a wrong evaluation of the risk of extinction.

Moreover, complete morphological information is absent as detailed above and this not affect only the taxonomy, but also conservation. For example, Diplodon pfeifferi (Dunker, 1848) is a species recorded only at the state of Rio de Janeiro and listed in 2008 edition of the Brazilian Red Book (Amaral et al. 2008AMARAL, A.C.Z., RIBEIRO, C.V., MANSUR, M.C.D., SANTOS, S.B., AVELAR, W.E.P., MATTHEWS-CASCON, H., LEITE, F.P.P., MELO, G.A.S., COELHO, P.A., BUCKUP, G.B., BUCKUP, L., VENTURA, C.R.R. & TIAGO, C.G. 2008. A situação de ameaça dos invertebrados aquáticos no Brasil. In Livro vermelho da fauna brasileira ameaçada de extinção (Machado, A.B.M., Drummond, G.M. & Paglia, A.P., orgs). Ministério do Meio Ambiente, Brasilia, p. 156-301.) but some authors include this species in the synonym of D. granosus (Simpson 1914SIMPSON, C.T. 1914. A descriptive catalogue of the Naiades or pearly freshwater mussels. Privately published by Bryant Walker, Michigan., Haas 1969HAAS, F. 1969. Superfamilia Unionacea. In Das Tierrich, Lieferung – vol 88 (Martens, R., Hennig W. & Wermuth, H., ed.). Walter de Gruyter and Co., Berlin., Simone 2006SIMONE, L.R.L. 2006. Land and freshwater molluscs of Brazil. EGB, Fapesp, São Paulo. 390pp.), a species not listed as threatened. It is clear that the correct identification of these two species is not only a problem of taxonomy.

It is necessary to improve the evaluation of risk to our mussels, some recommendations are done: 1) detail the distribution of the species relating, when possible, to environmental factors; 2) separate the old (or museum) records from current records; 3) collect in sub-sampled areas; 4) improve our knowledge on morphology and genetics to solve the taxonomical questions; 5) study the population dynamics of the species and 6) study the species reproduction cycle.

7. Summary of studies on Brazilian freshwater mussels

The first studies on South American Unionida fauna occurred during the time of great expeditions; several naturalists/collectors came to or received material from South America. One of the byproducts of this activity was that most part of South American type specimens are currently keep in European museums. Ironically, few species of naiads were described by South American researches, some exceptions are Bonetto (1962)BONETTO, A.A. 1962. Notas sobre Diplodon charruanus (Orb.) y Diplodon rhuacoicus (Orb.). Direccion General de Recursos Naturales – Publicación Técnica, Santa Fé., Bonetto & Tassara (1987)BONETTO, A.A. & TASSARA, M.P. 1987. Contribucion al conocimento de dos nayades sudamericanas. Rev. Mus. Argent. Cienc. Nat. Bernardino Rivadavia Inst. Nac. Invest. Cienc. Nat – Zool. 24(11): 163-170. and Mansur & Pimpão (2008)MANSUR, M.C.D. & PIMPÃO, D.M. 2008. Triplodon chodo, a new species of species of pearly fresh water mussel from Amazon Basin (Mollusca: Bivalvia: Unionoida: Hyriidae). Rev. Bras. Zool. 25(1): 111-115.. In this phase, the descriptions were based mainly on the shells and, the species nowadays recognized as Diplodon or Rhipidodonta, were placed in the genus Unio Retzius, 1788 and commonly any variation of the shell was described as a new species, resulting in a large number of species names.

To this descriptive phase, a new phase in the study of South American freshwater mussels followed, that encompassed the organization and analysis of these names, with the aim to determine what really correspond to a biological species. Ihering (1893)IHERING, H. 1893. Najaden von S. Paulo und die geographische verbreitung der süsswasserfauna von Südamerika. Arch. Naturgesch. 59: 45-140., a Deutsch zoologist established in Brazil, made the first attempt to organize some Brazilian species, and an improved work was published later (Ihering, 1910IHERING, H. 1910. Über brasilianische najaden. Abh. Senckenb. Naturforsch. Ges. 32: 111-140.). He also published a series of studies about Brazilian mussels (e.g.,Ihering, 1890IHERING, H. 1890. Revision der von Spix in Brasilien gesammelten najaden. Arch.Naturgesch. 56(1): 117-170., 1891IHERING, H. 1891. Anodonta und Glabaris. Zool. Anz. 14: 474-484.), including some specimens from little studied states of Brazil, like Goiás (Ihering, 1904IHERING, H. 1904. Zur kenntnis der najaden von Goyaz. Nachr.bl. Dtsch. Malakozool. Ges. 36(4): 154-157.). Morretes (1949)MORRETES, F.L. 1949. Ensaio do catálogo dos moluscos do Brasil. Arq. mus. Paranaense 7: 5-216. is the first catalogue about freshwater mussels of Brazil made by a Brazilian researcher. Marshall (1917MARSHALL, W.B. 1917. New and little now species of South American freshwater mussels of the genus Diplodon. Proc. U. S. Nat. Mus. 53(2209): 381-388., 1922MARSHALL, W.B. 1922. New pearly freshwater mussels from South America. Proc. U. S. Nat. Mus. 61(16): 1-9., 1923MARSHALL, W.B. 1923. New pearly freshwater mussels from Mexico and Uruguay. Proc. U. S. Nat. Mus. 63(16): 1-4., 1926MARSHALL, W.B. 1926. New land and freshwater mollusks from South America. Proc. U. S. Nat. Mus. 69(12): 1-12., 1927MARSHALL, W.B. 1927. A new genus and two new species of South American fresh-water mussels. Proc. U. S. Nat. Mus. 71(2): 1-4.) described a series of South American species and proposed two new genera, Diplodontites Marshall, 1922 and Mycetopodella, both still in use (Simone 2006SIMONE, L.R.L. 2006. Land and freshwater molluscs of Brazil. EGB, Fapesp, São Paulo. 390pp., Graf & Cummings 2007GRAF, D.L. & CUMMINGS, K.S. 2007. Review of the systematic and global diversity of freshwater mussel species (Bivalvia: Unionoida). J. Mollus. Stud. 73: 291-314.). Ortmann received a large amount of specimens from South America with soft parts that allowed him to describe new species and produced the above mentioned catalogue (Ortmann, 1921ORTMANN, A.E. 1921. South American naiades, a contribution to the knowledge of the fresh-water mussels of South America. Mem. Carnegie Mus. 8(3): 451-670.). Haas (1930HAAS, F. 1930. Versuch einer kritischen Sichtung der sudamerikanischen Najaden, hauptsachlich an Hand der Sammlung des Senckenberg-Museums I. Senckenbergiana, 12: 175–195., 1931aHAAS, F. 1931a. Versuch einer kritischen Sichtung der sudamerikanischen Najaden, hauptsachlich an Hand der Sammlung des Senckenberg-Museums II. Senckenbergiana, 13: 30–52.,bHAAS, F. 1931b. Versuch einer kritischen Sichtung der sudamerikanischen Najaden, hauptsachlich an Hand der Sammlung des Senckenberg-Museums III. Senckenbergiana, 13: 87–110.) published a catalog about South American species in a series of fully illustrated works. Haas (1969)HAAS, F. 1969. Superfamilia Unionacea. In Das Tierrich, Lieferung – vol 88 (Martens, R., Hennig W. & Wermuth, H., ed.). Walter de Gruyter and Co., Berlin. is a landmark in the study of freshwater bivalves not only in South America but also in the world, and remains as the most “modern” global catalog of Unionida species with synonymic lists. At the same time Cox et al. (1969)COX, L.R., NEWELL, N.D., BOYD, D.W., BRANSON, C.C., CASEY, R., CHAVAN, A., COOGAN, A.H., DECHASEAUX, C., FLEMING, C.A., HAAS, F., HERTLEIN, L.G., KAUFFMAN, E.G., KEEN, A.M., LAROCQUE, A., MCALESTER, A.L., MOORE, R.C., NUTTALL, C.P., PERKINS, B.F., PURI, H.S., SMITH, L.A., SOOT-RYEN, T., STENZEL, H.B., TRUEMAN, E.R., TURNER, R.D. & WEIR, J. 1969. Treatise on Invertebrate Paleontology – Part N, Volume 1 (of 3), Mollusca 6, Bivalvia. The Geological Society of America, Inc. and The University of Kansas. Kansas. presents a scheme including fossil groups.

The formation of South American freshwater mussel researches finally starts in the 1950’s. Argentino A. Bonetto from the 1950’s onwards published a series of papers concerning the mussel fauna of South America. From his extensive bibliography we can mention some of his studies about Rhipidodontini: dealing with diversity and anatomy (Bonetto 1954BONETTO, A.A. 1954. Nayades del rio Parana – el genero Diplodon en el biotope isleño del Parana medio e inferior. Secretaria de Agricultura, Ganaderia e Industrias – Publicación Tecnica, Santa Fé., 1962BONETTO, A.A. 1962. Notas sobre Diplodon charruanus (Orb.) y Diplodon rhuacoicus (Orb.). Direccion General de Recursos Naturales – Publicación Técnica, Santa Fé., 1964BONETTO, A.A. 1964. Las species del Género Diplodon (Moll. Unionacea) en los ríos de la pendiente Atlántica del sur del Brasil. Physis 24(68): 323-328., 1965BONETTO, A.A. 1965. Las especies del genero Diplodon en el sistema hidrografico del rio de La Plata. In Anais do II Congresso Latino-Americano de Zoologia (Guimarães, L.R. coord.) Departamento de Zoologia da Secretária de Agricultura, São Paulo, p.37-54., 1967BONETTO, A.A. 1967. La superfamilia Unionacea en la Cuenca Amazonica. In Atas do Simpósio sôbre a Biota Amazônica – Limnologia (Lent, H., ed.) Conselho Nacional de Pesquisas, Rio de Janeiro, p. 63-82., Bonetto & Mansur 1970BONETTO, A.A. & MANSUR, M.C.D. 1970. Las nayades de la Cuenca del Guaiba. Acta Zool. Lilloana 27: 241-260.), larval stages (Bonetto 1961BONETTO, A.A. 1961. Investigaciones acerca de las formas larvales en el genero “Diplodon” y su aplicacion a los studios sistematicos. Direccion General de Recursos Naturales – Publicación Técnica, Santa Fé., 1965BONETTO, A.A. 1965. Las especies del genero Diplodon en el sistema hidrografico del rio de La Plata. In Anais do II Congresso Latino-Americano de Zoologia (Guimarães, L.R. coord.) Departamento de Zoologia da Secretária de Agricultura, São Paulo, p.37-54., Bonetto & Ezcurra 1965BONETTO, A.A. & EZCURRA, I. 1965. Estudio comparado de las formas larvales de Mutelidae Ortmann y su significacion sistematica y zoogeografica. In Anais do II Congresso Latino-Americano de Zoologia (Guimarães, L.R. coord.) Departamento de Zoologia da Secretária de Agricultura, São Paulo, p. 55-71.), museum collection revision (Bonetto 1973BONETTO, A.A. 1973. Estudio revisivo de las colecciones de nayades de d´Orbigny existentes en el Museo Britanico. Sociedad Cientifica Argentina sección Santa Fé 1: 17-25.) and factors that affect mussel distribution (Bonetto et al. 1962BONETTO, A.A., MACIEL, I. & PIGNALBERI, C. 1962. Algunos factores ecologicos vinculados a la distribucion geografica de las nayades en el rio Parana y sus afluentes. Direccion General de Recursos Naturales– Publicación Técnica, Santa Fé, p.167-175., Bonetto & Di Persia 1975BONETTO, A.A. & DI PERSIA, D.H. 1975. Las poblaciones de pelecipodos del arroyo Ayui Grande (prov. Entre Rios) y los facores qye regulan sua distribucion y estrutura. Ecosur 2(3): 123-151.). The author also described two new species of Diplodon (Bonetto 1962BONETTO, A.A. 1962. Notas sobre Diplodon charruanus (Orb.) y Diplodon rhuacoicus (Orb.). Direccion General de Recursos Naturales – Publicación Técnica, Santa Fé., Bonetto & Tassara 1987BONETTO, A.A. & TASSARA, M.P. 1987. Contribucion al conocimento de dos nayades sudamericanas. Rev. Mus. Argent. Cienc. Nat. Bernardino Rivadavia Inst. Nac. Invest. Cienc. Nat – Zool. 24(11): 163-170.) and one subgenus (Bonetto et al. 1986BONETTO, A.A., TASSARA, M.P. & RUMI, A. 1986. Australis n. subgen. de Diplodon Spix (Bivalvia, Unionacea) y posibles relaciones con Hyriidae australianos. Bol. Soc. Biol. Concepc. 57: 55-61.).

Amongst the most important papers published by Juan J. Parodiz about mussels are the compendium of available names for Diplodon (Parodiz 1968PARODIZ, J.J. 1968. Annotated catalogue of the genus Diplodon (Unionacea – Hyriidae). Sterkiana 30: 1-22.) and a study about the hybridization of Diplodon delodontus (Parodiz 1973PARODIZ, J.J. 1973. The species complex of Diplodon delodontus (Lamarck) (Unionacea – Hyriidae). Malacologia 14: 247-270.). However, his masterpiece was the catalog about continental fossil molluscs (Parodiz 1969PARODIZ, J.J. 1969. The tertiary non-marine Mollusca of South America. Ann. Carnegie Mus. 40: 1-242.). Parodiz & Bonetto (1963)PARODIZ, J.J. & BONETTO, A.A. 1963. Taxonomy and Zoogeography relationships of the South American naiads (Pelecypoda: Unionacea and Mutelacea). Malacologia 1: 179-213. suggested a systematic arrangement of Unionida families based on larval type (see details above).

In Brazil, the studies of freshwater mussels intensified during the 1960’s. Zanardini (1965)ZANARDINI, I.F. 1965. Nota sôbre Diplodon e Anodontites (Mollusca-Pelecypoda) de rios de Curitiba (Paraná). Bol. Inst. Def. Patrim. Nat. Zool. 6: 1-11. published a note about the occurrence and distribution of Diplodon and Anodontites Bruguière, 1792 in the state of Paraná. A greater increase in knowledge about freshwater mussel fauna began with the works of Mansur (1970)MANSUR, M.C.D. 1970. Lista dos moluscos bivalves das famílias Hyriidae e Mycetopodidae para o estado do Rio Grande do Sul. Iheringia Ser. Zool. 39:33-95. that presented the catalog of Hyriidae and Mycetopodidae of the state of Rio Grande do Sul. She published works dealing with specimens from southern Brazil (Mansur 1972MANSUR, M.C.D. 1972. Morfologia do sistema digestivo de Castalia undosa martensi (Ihering, 1891) (Bivalvia: Hyriidae). Iheringia Ser. Zool.41: 21-34., 1973MANSUR, M.C.D. 1973. Morfologia do sistema digestivo das especies do gênero Diplodon Spix, 1827 do rio Guaíba, Rio Grande do Sul (Unionacea – Hyriidae). Iheringia Ser. Zool.43: 75-90., Mansur & Anflor 1982MANSUR, M.C.D. & ANFLOR, L.M. 1982. Diferenças morfológicas entre Diplodon charruanus (Orbigny, 1835) e D. pilsbry Marshall, 1928 (Bivalvia: Hyriidae). Iheringia Ser. Zool.60: 101-106., Mansur & Pereira 2006MANSUR, M.C.D. & PEREIRA, D. 2006. Bivalves límnicos da bacia do rio dos Sinos, Rio Grande do Sul, Brasil (Bivalvia, Unionoida, Veneroida e Mytiloida). Rev. Bras. Zool. 23(4): 1123-1147.) as well as from the Amazon River basin (Mansur & Valer 1992MANSUR, M.C.D. & VALER, R.M. 1992. Moluscos bivalves do Rio Uraricoera e Rio Branco, Roraima, Brasil. Amazoniana 12(1): 85-100., Mansur & Pimpão 2008MANSUR, M.C.D. & PIMPÃO, D.M. 2008. Triplodon chodo, a new species of species of pearly fresh water mussel from Amazon Basin (Mollusca: Bivalvia: Unionoida: Hyriidae). Rev. Bras. Zool. 25(1): 111-115., Pimpão & Mansur 2009PIMPÃO, D.M. & MANSUR, M.C.D. 2009. Chave pictórica para identificação dos bivalves do baixo rio Airupuanã, Amazonas, Brasil (Sphaeriidae, Hyriidae e Mycetopodidae). Biota Neotrop. 9: 1-8.) and Pantanal (Serrano et al. 1998SERRANO, M.A.S., TIETBÖHL, R.S. & MANSUR, M.C.D. 1998. Sobre a ocorrência de moluscos Bivalvia no pantanal de Mato Grosso, Brasil. Biociências 6(1): 131-144., Callil & Mansur 2005CALLIL, C.T. & MANSUR, M.C.D. 2005. Ultrastructural analysis of the shells of Anodontites trapesialis (Lamarck) and Anodontites elongatus (Swaison) (Mollusca, Bivalvia, Etherioidea) from the Mato Grosso Pantanal Region, Brazil. Rev. Bras. Zool. 22(3): 724-734., 2007CALLIL, C.T. & MANSUR, M.C.D. 2007. Gametogênese e dinâmica da reprodução de Anodontites trapesialis (Lamarck) (Unionoida, Mycetopodidae) no lago Baía do Poço, planície de inundação do rio Cuiabá, Mato Grosso, Brasil. Rev. Bras. Zool. 24: 825-840.). There are also two technical works, one identifying Southern and Southeastern genera of mussels (Mansur et al. 1987MANSUR, M.C.D., SCHULZ, C. & GARCES, L.M.M.P. 1987. Moluscos bivalves de água doce: identificação dos gêneros do sul e leste do Brasil. Acta Biol. Leopold. 9(2): 181-202.) and another on how to obtain and identify glochidia (Mansur & Campos-Velho 1991). Recently, her studies are mainly concerned with non-native bivalves (Mansur et al. 2012MANSUR, M.C.D., SANTOS, C.P., PEREIRA, D., PAZ, I.C.P., ZURITA, M.L.L., RODRIGUEZ, M.T.R., NEHRKE, M.V. & BERGONCI, P.E.A. 2012. Moluscos límnicos invasores no Brasil: biologia, prevenção e controle. Redes Editora, Porto Alegre.). The morphological aspects of Mycetopodidae were also studied in southern South America (Veitenheimer-Mendes 1973aVEITENHEIMER-MENDES, I.L. 1973a. Contribuição ao estudo do gênero Leila Gray, 1840 (Mycetopodidae: Bivalvia). Iheringia, Ser. Zool. 62(42): 64-89.,bVEITENHEIMER-MENDES, I.L. 1973b. Anodontites Bruguière, 1792 no Guaíba - RS (Mycetopodidae: Bivalvia). I – Anodontites trapesialias forbesianus (Lea, 1860). Iheringia, Ser. Zool. 62(44): 32-49., Veintenheimer-Mendes & Mansur 1978aVEINTENHEIMER-MENDES, I.L. & MANSUR, M.C.D. 1978a. Mycetopoda legumen: Lasídio e desenvolvimento parasitário (Bivalvia: Mycetopodidae). Rev. Bras. Biol. 38(3): 531-536.,bVEINTENHEIMER-MENDES, I.L. & MANSUR, M.C.D. 1978b. Morfologia, histologia e ecologia de Mycetopoda legumen (Martens, 1888) (Bivalvia: Mycetopodidae). Iheringia, Ser. Zool. 67(52): 33-71., 1979VEINTENHEIMER-MENDES, I.L. & MANSUR, M.C.D. 1979. Redescrição de Mycetopoda legumen (Martens, 1888)(Bivalvia: Mycetopodidae). Rev. Bras. Biol. 39(3): 695-702.).

Other researchers also studied freshwater mussels in Brazil. At the state of Rio de Janeiro, L.C. Alvarenga and C.N. Ricci studied the soft parts and glochidium of Diplodon multistriatus (Ricci et al. 1988RICCI, C.N., COELHO, A.C.S & ALVARENGA, L.C.F. 1988. Diplodon (D.) multistriatus (Lea, 1831): Concha, partes moles e considerações taxonômicas (Mollusca, Bivalvia, Hyriidae). Bol. Mus. Nac. Zool. 325: 1-19., 1990RICCI, C.N., ALVARENGA, L.C.F. & COELHO, A.C.S. 1990. Gloquídios de Diplodon Spix, 1827: D. (D.) multistriatus (Lea, 1831) (Mollusca, Bivalvia, Hyriidae). Bol. Mus. Nac. Zool. 344: 1-10.), as well as the morphology of soft parts, glochidium and shell variation of Diplodon besckeanus (Alvarenga & Ricci 1977aALVARENGA, L.C.F. & RICCI, C. 1977a. Contribuição ao conhecimento dos gloquídios do gênero Diplodon Spix, 1827: D. besckeanus (Dunker, 1849) (Bivalvia: Unionoidea: Hyriidae). Anais do V Encontro de Malacologistas Brasileiros 33-38.,bALVARENGA, L.C.F. & RICCI, C. 1977b. Variações morfológicas encontradas nas conchas de uma população de Diplodon besckeanus (Dunker, 1849) (Bivalvia: Unionoidea: Hyriidae). Anais do V Encontro de Malacologistas Brasileiros 41-53., 1981ALVARENGA, L.C.F. & RICCI, C. 1981. Morfologia das partes moles de Diplodon (D.) besckeanus (Dunker, 1849) (Bivalvia, Unionoidea, Hyriidae). Bol. Mus. Nac., Zool. 298: 1-8.). In the field of functional anatomy, there are the works of Wagner Avelar (Avelar & Santos 1992AVELAR, W.E.P. & SANTOS, S.C.D. 1992. Functional morfology of Castalia undosa undosa (Martens, 1827) Bivalvia Hyriidae. Velinger 34: 21-31., Avelar 1993AVELAR, W.E.P. 1993. Funcional anatomy of Fossula fossiculifera (D'Orbigny 1843) Bivalvia Mycetopodidae. Am. Malacol. Bull. 10: 129-138., Avelar & Cunha 2009AVELAR, W.E.P. & CUNHA, A.D. 2009. The anatomy and functional morphology of Diplodon rhombeus fontainianus (Orbigny, 1835) (Mollusca, Bivalvia, Hyriidae). Braz. J. Biol. 69(4):1153-1163.) and Nilton Hebling (Hebling & Penteado 1974HEBLING, N.J. & PENTEADO, A.M.G. 1974. Anatomia functional de Diplodon rotundus gratus Wagner, 1827 (Mollusca, Bivalvia). Rev. Bras. Biol. 34(1): 67-80., Hebling 1976HEBLING, N.J. 1976. The functional morphology of Anodontites trapezeus (Spix) and Anodontites trapesialis (Lamarck) (Bivalvia: Mycetopodidae). Bol. Zool. Univ. São Paulo 1: 265-298.) concerning Hyriidae and Mycetopodidae species. Simone (1994SIMONE, L.R.L. 1994. Anatomical characters and systematics of Anodontites trapesialis (Lamarck, 1819) from South America (Mollusca, Bivalvia, Unionoida, Muteloidea). Stud. Neotrop. Fauna Environ. 29(3): 169-185., 1997SIMONE, L.R.L. 1997. Anatomy and systematics of Anodontites elongatus (Swainson) from Amazon and Paraná basins, Brazil (Mollusca, Bivalvia, Unionoida, Mycetopodidae). Rev. Bras. Zool. 14(4): 877-888.) described the morphology of two species of Anodontites. Simone (2006)SIMONE, L.R.L. 2006. Land and freshwater molluscs of Brazil. EGB, Fapesp, São Paulo. 390pp. published an illustrated catalogue of molluscs species of Brazil (details above).

There are few studies on ecology, population dynamics and reproduction in Brazil. As the taxonomic and systematic issues have not been properly handled for most species, this often becomes an obstacle for ecological approaches. Henry & Simão (1985)HENRY, R. & SIMÃO, C.A. 1985. Spatial distribution of a bivalve population (Diplodon delodontus expansus) (Küster, 1856) in a small tropical reservoir. Rev. Bras. Biol. 45(4): 407-415. analyzed the distribution of a population of Diplodon delodontus expansus (Küster, 1856) in the state of São Paulo. Beasley (2001)BEASLEY, C.R. 2001. The impact of explotation on freshwater mussels (Bivalvia: Hyriidae) in the Tocantins river, Brazil. Stud. Neotrop. Fauna 36(2): 159-165. presents strategies for managing hyriids from the Amazon River basin. Meyer et al. (2010)MEYER, A.A.N., OLIVEIRA, E. & MARTIM, J. 2010. Classes de comprimento e proporção sexual em Diplodon expansus (Mollusca, Bivalvia, Hyriidae) no rio Piraquara, Paraná, Brasil. Iheringia Ser. Zool. 100(4): 329-335. evaluated the population structure and sexual proportion in a population of Diplodon expansus. Beasley et al. (2005)BEASLEY, C.R., MIRANDA, L.Q., ALVES, S.T.M., MELO, A.G., SOUZA, J.O. & TAGLIARO, C.H. 2005. Brood size and larval length of Paxyodon syrmatophorus (Bivalvia, Hyriidae) from the Tocantins river, Brazil. Amazoniana 18(3/4): 173-184. presented the reproductive cycle of Paxyodon syrmatophorus (Meuschen, 1781), while Avelar & Mendonça (1998)AVELAR, W.E.P. & MENDONÇA, S.H.S. 1998. Aspects of gametogenesis of Diplodon rotundus gratus (Wagner,1827) (Bivalvia Hyriidae). Am. Malacol. Bull. 14(2): 157-165. presented the gametogenesis of Diplodon rotundus gratus. Tomazelli et al. (2003)TOMAZELLI, A.C., MARTINELLI, L.A., AVELAR, W.E.P., CAMARGO, P.B., FOSTIER, A., FERRAZ, E.S.B., KRUG, F.J. & JÚNIOR, D.S. 2003. Biomonitoring of Pb and Cd in two impacted watersheds in southeast Brazil, using the freshwater mussel Anodontites trapesialis (Lamarck, 1819) (Bivalvia: Mycetopodidae) as a biological monitor. Braz. Arch. Biol. Technol. 46(4): 673-684. suggested the potential use of A. trapesialis as biological sentinel and the life cycle of this species were investigated by Callil & Mansur (2007)CALLIL, C.T. & MANSUR, M.C.D. 2007. Gametogênese e dinâmica da reprodução de Anodontites trapesialis (Lamarck) (Unionoida, Mycetopodidae) no lago Baía do Poço, planície de inundação do rio Cuiabá, Mato Grosso, Brasil. Rev. Bras. Zool. 24: 825-840. and Callil et al (2012)CALLIL, C.T., KRINSKI, D. & SILVA, F.A. 2012. Variations of the larval incubation of Anodontites trapesialis (Unionoida, Mycetopodidae): Synergetic effect of the environmental factors and host availability. Braz. J. Biol. 72(3): 545-552.. Lopes et al. (2011)LOPES, L.P., PIMPÃO, D.M., TAKEMOTO, R.M., MALTA, J.C. & VARELLA, A.M. 2011. Hysterothylacium larvae (Nematoda, Anisakidae) in the freshwater mussel Diplodon suavidicus (Lea, 1856) (Mollusca, Unioniformes, Hyriidae) in Aripuanã River, Amazon, Brazil. J. Invertebr. Pathol. 106(3): 357-359. identified the parasite interaction in Diplodon suavidicus parasited by Hysterothylacium sp. (Nematoda). Recently the first phylogenetic approach of Hyriidae in Brazil was presented by Santos-Neto et al. (2016)SANTOS-NETO, G.C., BEASLEY, C.R., SCHNEIDER, H., PIMPÃO, D.M., HOEH, W.R., SIMONE, L.R.L. & TAGLIARO, C.H. 2016. Genetic relationships among freshwater mussel species from fifteen Amazonian rivers and inferences on the evolution of the Hyriidae (Mollusca: Bivalvia: Unionoida). Mol. Phylogenet. Evol. 100: 148-159..

Important faunal surveys about freshwater mussels exist in other South American countries: French Guyana (Drouet 1859DROUET, H. 1859. Essai sur les mollusques terrestres et fluviátiles de la Guyane Française. JB Baillière, Libraire de L’Académie de Médecine, Paris., Massemin et al. 2010MASSEMIN, D., LAMY, D., POINTIER, J.P. & GARGOMINY, O. 2010. Coquillages et Escargots de Guyane. 456 pp.), Suriname (Verhout 1914VERNHOUT, J.H. 1914. The non-marine molluscs of Surinam. I. Notes Leyden Mus. 36: 1-46.), Venezuela (Baker 1930BAKER, H.B. 1930. The Mollusca collected by the University of Michigan – Williamson Expedition in Venezuela. Part VI. Occas. pap. Mus. Zool. Univ. Mich. 9(210): 1-95., Lasso et al. 2009LASSO, C.A., MARTÍNEZ-ESCARBASSIERE, R., CAPELO, J.C., MORALES-BETANCOURT, M.A. & SÁNCHEZ-MAYA, A. 2009. Lista de los moluscos (Gastropoda-Bivalvia) dulceacuícolas y estuarinos de la cuenca del Orinoco (Venezuela). Biot. Colombiana 10(1/2): 63-74., Cummings & Mayer 2011CUMMINGS, K.C. & MAYER, C.A. 2011. The Freshwater Mussels (Bivalvia: Etherioidea) of Venezuela. http://www.inhs.uiuc.edu/animals_plants/mollusk/SA/Ven.html. (last acess in February/2017).
http://www.inhs.uiuc.edu/animals_plants/...
), Peru (Ramírez et al. 2003RAMÍREZ, R., PAREDES, C. & ARENAS, J. 2003. Moluscos del Perú. Rev. Biol. Trop. 51(Suppl. 3): 225-284.), Paraguay (Quintana 1982QUINTANA, M.G. 1982. Catalogo preliminar de la malacofauna del Paraguay. Rev. Mus. Argent. Cienc. Nat. Bernardino Rivadavia, Zool. 11: 61-158.), Argentina (Rumi et al. 2008RUMI, A., GREGORIC, D.E.G., NÚÑEZ, V. & DARRIGRAN, G.A. 2008. Malacologia Latinoamericana - Moluscos de agua dulce de Argentina. Rev. Biol. Trop. 56(1): 77-111.), Uruguay (Corsi 1901CORSI, A.F. 1901. Molluscos de la Rupublica Oriental del Uruguay. Anales Mus. Nac. Montevideo 2: 295-499., Olazarri 1966OLAZARRI, J. 1966. Los moluscos de Agua Dulce Del Depto. de Colonia, Uruguay. Part I: Pelecypoda. Comun. Soc. Malacol. Urug. 2(11): 15-37., Scarabino & Mansur 2007SCARABINO, F. & MANSUR, M.C.D. 2007. Lista sistematica de los Bivalvia dulciacuícolas viventes de Uruguay. Comun. Soc. Malacol. Urug. 9(90): 89-99., Clavijo 2009CLAVIJO, C. 2009. Distribución del género Anodontites (Mollusca: Bivalvia: Mycetopodidae) en Uruguay. Comun. Soc. Malacol. Urug. 9(92): 201-210.) and Chile (Parada & Peredo 2002PARADA, E. & PEREDO, S. 2002. Estado actual de la taxonomía de bivalvos dulceacuícolas chilenos: progresos y conflictos. Rev. Chil. Hist. Nat. 75: 691-701.).

8. Conclusions

The large number of works concerning freshwater mussels in South America can give a false idea that the knowledge about these species is deep, but most of works are discreet and deal with one or two species. Comparative approaches of all kinds (morphological, ecological or molecular) are virtually absent. Even basic information is missing, as many species have not been studied beyond the original description. There have been some recent advances in Unionida systematic and the scheme with six or five families looks well established. However, the relationships inside the groups (e.g., families, genera) are poorly known and Rhipidodontini is not an exception. More data were needed to a better comprehension of the species and try to definitively solve questions like the status of Rhipidodonta. It is also an important step in order to reveal the real diversity of this group. The absence of good taxonomic and systematic information has been a limiting factor for biological and ecological studies, preventing appropriated extinction risk evaluation. The interactions of native with the invasive species need to be better understood, considering that the dispersion of the latter is notorious and harmful for native species. Integrating all this information is essential to development of appropriate conservation strategies for freshwater mussels in South America.

Supplementary material

The following online material is available for this article:

Appendix 1– Taxonomical arrangement of principal revisions of Rhipidodontini. E – species; SE – subspecies; NA – not used by the author as species or subspecies.

Acknowledgments

Our gratitude goes to CNPq/PROTAX (562291/2010-5) for financial support to SBS and scholarship to ICM; to the curators of MNRJ, MHNM, ZMB, SMF and LDM for the support during the museum surveys; to the two anonymous reviewers that contributed to improve the manuscript.

References

  • ALVARENGA, L.C.F. & RICCI, C. 1977a. Contribuição ao conhecimento dos gloquídios do gênero Diplodon Spix, 1827: D. besckeanus (Dunker, 1849) (Bivalvia: Unionoidea: Hyriidae). Anais do V Encontro de Malacologistas Brasileiros 33-38.
  • ALVARENGA, L.C.F. & RICCI, C. 1977b. Variações morfológicas encontradas nas conchas de uma população de Diplodon besckeanus (Dunker, 1849) (Bivalvia: Unionoidea: Hyriidae). Anais do V Encontro de Malacologistas Brasileiros 41-53.
  • ALVARENGA, L.C.F. & RICCI, C. 1981. Morfologia das partes moles de Diplodon (D.) besckeanus (Dunker, 1849) (Bivalvia, Unionoidea, Hyriidae). Bol. Mus. Nac., Zool. 298: 1-8.
  • AMARAL, A.C.Z., RIBEIRO, C.V., MANSUR, M.C.D., SANTOS, S.B., AVELAR, W.E.P., MATTHEWS-CASCON, H., LEITE, F.P.P., MELO, G.A.S., COELHO, P.A., BUCKUP, G.B., BUCKUP, L., VENTURA, C.R.R. & TIAGO, C.G. 2008. A situação de ameaça dos invertebrados aquáticos no Brasil. In Livro vermelho da fauna brasileira ameaçada de extinção (Machado, A.B.M., Drummond, G.M. & Paglia, A.P., orgs). Ministério do Meio Ambiente, Brasilia, p. 156-301.
  • ARTEAGA-SOGAMOSO, E. 1994. El lasidium de Acostaea rivoli Deshayes, 1827 (Mollusca; Bivalvia-Etheriidae) y su importancia para la ubicación taxonômica de esta espécie. Bol. ecotropica 27: 1-9.
  • AVELAR, W.E.P. 1993. Funcional anatomy of Fossula fossiculifera (D'Orbigny 1843) Bivalvia Mycetopodidae. Am. Malacol. Bull. 10: 129-138.
  • AVELAR, W.E.P. & SANTOS, S.C.D. 1992. Functional morfology of Castalia undosa undosa (Martens, 1827) Bivalvia Hyriidae. Velinger 34: 21-31.
  • AVELAR, W.E.P. & MENDONÇA, S.H.S. 1998. Aspects of gametogenesis of Diplodon rotundus gratus (Wagner,1827) (Bivalvia Hyriidae). Am. Malacol. Bull. 14(2): 157-165.
  • AVELAR, W.E.P. & CUNHA, A.D. 2009. The anatomy and functional morphology of Diplodon rhombeus fontainianus (Orbigny, 1835) (Mollusca, Bivalvia, Hyriidae). Braz. J. Biol. 69(4):1153-1163.
  • BAKER, H.B. 1930. The Mollusca collected by the University of Michigan – Williamson Expedition in Venezuela. Part VI. Occas. pap. Mus. Zool. Univ. Mich. 9(210): 1-95.
  • BEASLEY, C.R. 2001. The impact of explotation on freshwater mussels (Bivalvia: Hyriidae) in the Tocantins river, Brazil. Stud. Neotrop. Fauna 36(2): 159-165.
  • BEASLEY, C.R., MIRANDA, L.Q., ALVES, S.T.M., MELO, A.G., SOUZA, J.O. & TAGLIARO, C.H. 2005. Brood size and larval length of Paxyodon syrmatophorus (Bivalvia, Hyriidae) from the Tocantins river, Brazil. Amazoniana 18(3/4): 173-184.
  • BIELER, R. & MIKKELSEN, A.P.M. 2006. Bivalvia – a look at the branches. Zool. J. Linnean Soc. 148: 223-235.
  • BIELER, R., CARTER, J.G. COAN, E.V. 2010. Classification of bivalve families. Malacologia 52(2): 113-184.
  • BIELER, R., MIKKELSEN, P.M.; COLLINS, T.M., GLOVER, E.A., GONZÁLEZ, V.L., GRAF, D.L., HARPER, E.M., HEALY, J., KAWAUCHI, G.Y., SHARMA, P.P., STAUBACH, S., STRONG, E.E., TAYLOR, J.D., TËMKIN, I., ZARDUS, J.D., CLARK, S., GUZMÁN, A., McINTYRE, E., SHARP, P. & GIRIBET, G. 2014. Investigating the Bivalve Tree of Life – an exemplar-based approach combining molecular and novel morphological characters. Invertebrate Systematics 28: 32-115.
  • BOGAN, A.E. 2008. Global diversity of freshwater mussels (Mollusca, Bivalvia) in freshwater. Hydrobiologia 595: 139-147.
  • BOGAN, A.E. & HOEH, W.R. 2000. On becoming cemented: evolutionary relationships among the genera in the freshwater familiy Etheriidae (Bivalvia: Unionoida). In The evolutionary biology of the Bivalvia (Harper, E.M.; Taylor, J.D. & Crame, J., eds). Geological Society, London, London, p.159-168.
  • BOGAN, A.E. & ROE, K.J. 2008. Freshwater bivalve (Unioniformes) diversity, systematics, and evolution: status and future directions. J. North Am. Benthol. Soc. 27(2):349-369.
  • BOLTOVSKOY, D. & CORREA, N. 2015. Ecosystem impacts of the invasive bivalve Limnoperna fortunei (golden mussel) in South America. Hydrobiologia 746: 81-95.
  • BONETTO, A.A. 1954. Nayades del rio Parana – el genero Diplodon en el biotope isleño del Parana medio e inferior. Secretaria de Agricultura, Ganaderia e Industrias – Publicación Tecnica, Santa Fé.
  • BONETTO, A.A. 1961. Investigaciones acerca de las formas larvales en el genero “Diplodon” y su aplicacion a los studios sistematicos. Direccion General de Recursos Naturales – Publicación Técnica, Santa Fé.
  • BONETTO, A.A. 1962. Notas sobre Diplodon charruanus (Orb.) y Diplodon rhuacoicus (Orb.). Direccion General de Recursos Naturales – Publicación Técnica, Santa Fé.
  • BONETTO, A.A. 1964. Las species del Género Diplodon (Moll. Unionacea) en los ríos de la pendiente Atlántica del sur del Brasil. Physis 24(68): 323-328.
  • BONETTO, A.A. 1965. Las especies del genero Diplodon en el sistema hidrografico del rio de La Plata. In Anais do II Congresso Latino-Americano de Zoologia (Guimarães, L.R. coord.) Departamento de Zoologia da Secretária de Agricultura, São Paulo, p.37-54.
  • BONETTO, A.A. 1967. La superfamilia Unionacea en la Cuenca Amazonica. In Atas do Simpósio sôbre a Biota Amazônica – Limnologia (Lent, H., ed.) Conselho Nacional de Pesquisas, Rio de Janeiro, p. 63-82.
  • BONETTO, A.A. 1973. Estudio revisivo de las colecciones de nayades de d´Orbigny existentes en el Museo Britanico. Sociedad Cientifica Argentina sección Santa Fé 1: 17-25.
  • BONETTO, A.A. 1997. Las “ostras de agua dulce” (Muteloidea: Mutelidae). Su taxonomía y distribución geográfica en el conjunto de las naiades del mundo. Biociências 5(1): 113-142.
  • BONETTO, A.A., MACIEL, I. & PIGNALBERI, C. 1962. Algunos factores ecologicos vinculados a la distribucion geografica de las nayades en el rio Parana y sus afluentes. Direccion General de Recursos Naturales– Publicación Técnica, Santa Fé, p.167-175.
  • BONETTO, A.A. & EZCURRA, I. 1965. Estudio comparado de las formas larvales de Mutelidae Ortmann y su significacion sistematica y zoogeografica. In Anais do II Congresso Latino-Americano de Zoologia (Guimarães, L.R. coord.) Departamento de Zoologia da Secretária de Agricultura, São Paulo, p. 55-71.
  • BONETTO, A.A. & MANSUR, M.C.D. 1970. Las nayades de la Cuenca del Guaiba. Acta Zool. Lilloana 27: 241-260.
  • BONETTO, A.A. & DI PERSIA, D.H. 1975. Las poblaciones de pelecipodos del arroyo Ayui Grande (prov. Entre Rios) y los facores qye regulan sua distribucion y estrutura. Ecosur 2(3): 123-151.
  • BONETTO, A.A., TASSARA, M.P. & RUMI, A. 1986. Australis n. subgen. de Diplodon Spix (Bivalvia, Unionacea) y posibles relaciones con Hyriidae australianos. Bol. Soc. Biol. Concepc. 57: 55-61.
  • BONETTO, A.A. & TASSARA, M.P. 1987. Contribucion al conocimento de dos nayades sudamericanas. Rev. Mus. Argent. Cienc. Nat. Bernardino Rivadavia Inst. Nac. Invest. Cienc. Nat – Zool. 24(11): 163-170.
  • CALLIL, C.T. & MANSUR, M.C.D. 2005. Ultrastructural analysis of the shells of Anodontites trapesialis (Lamarck) and Anodontites elongatus (Swaison) (Mollusca, Bivalvia, Etherioidea) from the Mato Grosso Pantanal Region, Brazil. Rev. Bras. Zool. 22(3): 724-734.
  • CALLIL, C.T. & MANSUR, M.C.D. 2007. Gametogênese e dinâmica da reprodução de Anodontites trapesialis (Lamarck) (Unionoida, Mycetopodidae) no lago Baía do Poço, planície de inundação do rio Cuiabá, Mato Grosso, Brasil. Rev. Bras. Zool. 24: 825-840.
  • CALLIL, C.T., KRINSKI, D. & SILVA, F.A. 2012. Variations of the larval incubation of Anodontites trapesialis (Unionoida, Mycetopodidae): Synergetic effect of the environmental factors and host availability. Braz. J. Biol. 72(3): 545-552.
  • CAMPBELL, J.D., COOMBS, D.S. & GREBNEFF, A. 2003. Willsher group and geology of the Triassic Kaka Point coastal section, south-east Otago, New Zeland. J. R. Soc. N. Z. 33: 7-38.
  • CLAVIJO, C. 2009. Distribución del género Anodontites (Mollusca: Bivalvia: Mycetopodidae) en Uruguay. Comun. Soc. Malacol. Urug. 9(92): 201-210.
  • CLAVIJO, C. 2017. The Pearl industry and pioneering research in biology and conservation of pearl mussels (Unionoida) in the Río de La Plata Basin. Tentacle 25: 14-15.
  • CORSI, A.F. 1901. Molluscos de la Rupublica Oriental del Uruguay. Anales Mus. Nac. Montevideo 2: 295-499.
  • COX, L.R., NEWELL, N.D., BOYD, D.W., BRANSON, C.C., CASEY, R., CHAVAN, A., COOGAN, A.H., DECHASEAUX, C., FLEMING, C.A., HAAS, F., HERTLEIN, L.G., KAUFFMAN, E.G., KEEN, A.M., LAROCQUE, A., MCALESTER, A.L., MOORE, R.C., NUTTALL, C.P., PERKINS, B.F., PURI, H.S., SMITH, L.A., SOOT-RYEN, T., STENZEL, H.B., TRUEMAN, E.R., TURNER, R.D. & WEIR, J. 1969. Treatise on Invertebrate Paleontology – Part N, Volume 1 (of 3), Mollusca 6, Bivalvia. The Geological Society of America, Inc. and The University of Kansas. Kansas.
  • CUMMINGS, K.C. & MAYER, C.A. 2011. The Freshwater Mussels (Bivalvia: Etherioidea) of Venezuela. http://www.inhs.uiuc.edu/animals_plants/mollusk/SA/Ven.html (last acess in February/2017).
    » http://www.inhs.uiuc.edu/animals_plants/mollusk/SA/Ven.html
  • DARRIGRAN, G. & DAMBORENEA, C. 2006. Bio-invasión del mejillón dorado en el continente americano. Editorial de la Universidad de La Plata. La Plata, La Plata.
  • DARRIGRAN, G., DAMBORENEA, C. & GRECO, N. 2007. Freshwater invasive bivalves in man-made environments: A case study of larvae biology of Limnoperna fortunei in a Hydroelectric Power Plant in South America. AMBIO, 36(7):575-579
  • DROUET, H. 1859. Essai sur les mollusques terrestres et fluviátiles de la Guyane Française. JB Baillière, Libraire de L’Académie de Médecine, Paris.
  • FRANC, 1960. Classe des Bivalves. In: Traité de Zoologie – Tome V, Fascicule II (Grassé, P.P., Ed.) Masson et cie Éditeurs, Paris. p.1855-2164p.
  • GIRIBET, G. 2008. Bivalvia. In Phylogeny and evolution of the Mollusca (Ponder, W.F. & Lindberg, D.R., eds). University of Carolina Press, Berkeley, p.105-141.
  • GRAF, D.L. 2000. The Etherioidea revisited: a phylogenetic analysis of Hyriid relationships (Mollusca: Bivalvia: Paleoheterodonta: Unionoida). Occas. pap. Mus. Zool. Univ. Mich. 729: 1-21.
  • GRAF, D.L. & CUMMINGS, K.S. 2006. Paleoheterodont diversity (Mollusca: Trigonoida + Unionoida): what we know and what we wish we knew about freshwater mussel evolution. Zool. J. Linnean Soc. 148: 343-394.
  • GRAF, D.L. & CUMMINGS, K.S. 2007. Review of the systematic and global diversity of freshwater mussel species (Bivalvia: Unionoida). J. Mollus. Stud. 73: 291-314.
  • GRAF, D.L., JONES, H., GENEVA, A.J.; PFEIFER III, J.M. & KLUNZINGER, M.W. 2015. Molecular phylogenetics analysis supports a Gondwanan origin of the Hyriidae (Mollusca: Bivalvia: Unionoida) and the paraphyly of Australasian taxa. Mol. Phylogenet. Evol. 85: 1-9.
  • HAAG, W.R. 2012. North American freshwater mussels: natural history, ecology and conservation. Cambridge University Press, Cambridge.
  • HAAS, F. 1916. Nayades del viaje al Pacifico. Trabajos Mus. Nacion. Cienc. Nat., Madrid, (Zool.) 25:1-63.
  • HAAS, F. 1929. Beitrag zur Kenntnis der südamerikanischen Binnenmollusken. Senckenbergiana Biol. 11(:8-13.
  • HAAS, F. 1930. Versuch einer kritischen Sichtung der sudamerikanischen Najaden, hauptsachlich an Hand der Sammlung des Senckenberg-Museums I. Senckenbergiana, 12: 175–195.
  • HAAS, F. 1931a. Versuch einer kritischen Sichtung der sudamerikanischen Najaden, hauptsachlich an Hand der Sammlung des Senckenberg-Museums II. Senckenbergiana, 13: 30–52.
  • HAAS, F. 1931b. Versuch einer kritischen Sichtung der sudamerikanischen Najaden, hauptsachlich an Hand der Sammlung des Senckenberg-Museums III. Senckenbergiana, 13: 87–110.
  • HAAS, F. 1938. Neue Binnen-Mollusken aus Nordost-Brasilien. Arch. Moll. 70: 46-51.
  • HAAS, F. 1966. On some new non-marine mollusks from Colombia and Peru. Fieldiana Zool. 44(25):231-240.
  • HAAS, F. 1969. Superfamilia Unionacea. In Das Tierrich, Lieferung – vol 88 (Martens, R., Hennig W. & Wermuth, H., ed.). Walter de Gruyter and Co., Berlin.
  • HEBLING, N.J. 1976. The functional morphology of Anodontites trapezeus (Spix) and Anodontites trapesialis (Lamarck) (Bivalvia: Mycetopodidae). Bol. Zool. Univ. São Paulo 1: 265-298.
  • HEBLING, N.J. & PENTEADO, A.M.G. 1974. Anatomia functional de Diplodon rotundus gratus Wagner, 1827 (Mollusca, Bivalvia). Rev. Bras. Biol. 34(1): 67-80.
  • HENRY, R. & SIMÃO, C.A. 1985. Spatial distribution of a bivalve population (Diplodon delodontus expansus) (Küster, 1856) in a small tropical reservoir. Rev. Bras. Biol. 45(4): 407-415.
  • HOEH, W.R. & BOGAN, A.E. 2000. On becoming cemented: evolutionary relationships among the genera in freshwater bivalve family Etheriidae (Bivalvia: Unionoida). In: Harper, E.M., Taylor, J.D. Cramer, J.A. (eds) The evolutionary biology of the Bivalvia. Geological Society, London. p. 159-168.
  • HOEH, W.R., BOGAN, A.E. & HEARD, W.H. 2001. A phylogenetic perspective on the evolution of morphological and reproductive characteristics in the Unionoida. In: Bauer, G. & Wächtler, K. (eds.) Evolution of the freshwater mussels Unionoida. Springer-Verlag, Berlin.
  • HOEH, W.R., BOGAN, A.E., HEARD, W.H. & CHAPMAN, E.G., 2009. Paleoheterodont phylogeny, character evolution, diversity and phylogenetic classification: a reflection of method of analysis. Malacologia 51: 307-317.
  • IHERING, H. 1890. Revision der von Spix in Brasilien gesammelten najaden. Arch.Naturgesch. 56(1): 117-170.
  • IHERING, H. 1891. Anodonta und Glabaris Zool. Anz. 14: 474-484.
  • IHERING, H. 1893. Najaden von S. Paulo und die geographische verbreitung der süsswasserfauna von Südamerika. Arch. Naturgesch. 59: 45-140.
  • IHERING, H. 1904. Zur kenntnis der najaden von Goyaz. Nachr.bl. Dtsch. Malakozool. Ges. 36(4): 154-157.
  • IHERING, H. 1910. Über brasilianische najaden. Abh. Senckenb. Naturforsch. Ges. 32: 111-140.
  • KABAT, A.R. 1997. Correct family names for the freshwater “Muteloid” bivalves (Unionoida: Etherioidea). Occas. pap. mollusks 5(72): 379-392.
  • LASSO, C.A., MARTÍNEZ-ESCARBASSIERE, R., CAPELO, J.C., MORALES-BETANCOURT, M.A. & SÁNCHEZ-MAYA, A. 2009. Lista de los moluscos (Gastropoda-Bivalvia) dulceacuícolas y estuarinos de la cuenca del Orinoco (Venezuela). Biot. Colombiana 10(1/2): 63-74.
  • LEA, I. 1836. A synopsis of the family of naiades. Cary, Lea and Blanchard, Philadelphia.
  • LOPES, L.P., PIMPÃO, D.M., TAKEMOTO, R.M., MALTA, J.C. & VARELLA, A.M. 2011. Hysterothylacium larvae (Nematoda, Anisakidae) in the freshwater mussel Diplodon suavidicus (Lea, 1856) (Mollusca, Unioniformes, Hyriidae) in Aripuanã River, Amazon, Brazil. J. Invertebr. Pathol. 106(3): 357-359.
  • MANSUR, M.C.D. 1970. Lista dos moluscos bivalves das famílias Hyriidae e Mycetopodidae para o estado do Rio Grande do Sul. Iheringia Ser. Zool. 39:33-95.
  • MANSUR, M.C.D. 1972. Morfologia do sistema digestivo de Castalia undosa martensi (Ihering, 1891) (Bivalvia: Hyriidae). Iheringia Ser. Zool.41: 21-34.
  • MANSUR, M.C.D. 1973. Morfologia do sistema digestivo das especies do gênero Diplodon Spix, 1827 do rio Guaíba, Rio Grande do Sul (Unionacea – Hyriidae). Iheringia Ser. Zool.43: 75-90.
  • MANSUR, M.C.D. 1999. Gloquídio de Diplodon martensi (Ihering) (Mollusca, Bivalvia, Hyriidae) e seu ciclo parasitário. Rev. Bras. Zool. 16(Supl. 2): 185-194.
  • MANSUR, M.C.D. 2007. Moluscos da classe Bivalvia que tiveram sucesso ao se irradiarem no ambiente de água doce. 27-29p. In: Livro de Resumos do XX Encontro Brasileiro de Malacologia, Rio de Janeiro. 406pp.
  • MANSUR, M.C.D. & ANFLOR, L.M. 1982. Diferenças morfológicas entre Diplodon charruanus (Orbigny, 1835) e D. pilsbry Marshall, 1928 (Bivalvia: Hyriidae). Iheringia Ser. Zool.60: 101-106.
  • MANSUR, M.C.D., SCHULZ, C. & GARCES, L.M.M.P. 1987. Moluscos bivalves de água doce: identificação dos gêneros do sul e leste do Brasil. Acta Biol. Leopold. 9(2): 181-202.
  • MANSUR, M.C.D. & CAMPOS-VELHO, N.M.R. 1990. Técnicas para o estudo dos gloquídios de Hyriidae (Mollusca, Bivalvia, Unionoida). Acta Biol. Leopold. 12(1): 5-18.
  • MANSUR, M.C.D. & VALER, R.M. 1992. Moluscos bivalves do Rio Uraricoera e Rio Branco, Roraima, Brasil. Amazoniana 12(1): 85-100.
  • MANSUR, M.C.D. & SILVA, M.G.O. 1999. Description of glochidia of five species of freshwater mussels (Hyriidae: Unionoidea) from South America. Malacologia 41(2): 475-483.
  • MANSUR, M.C.D., QUEVEDO, C.B., SANTOS, C.P. & CALLIL, C.T. 2004a. Provavéis vias de introdução de Limnoperna fortunei (Dunker, 1857) (Mollusca, Bivalvia, Mytilidae) na bacia da Laguna dos Patos, Rio Grande do Sul e novos registros de invasão no Brasil pelas bacias do Paraná e Paraguai. In Água de lastro e bioinvasão (Silva, J.S.V. & Souza, R.C.C.L, orgs) Editora Interciência, Rio de Janeiro, p. 33-38.
  • MANSUR, M.C.D., CALLIL, C.T., CARDOSO, F.R. & IBARRA, J.A.A. 2004b. Uma retrospectiva e mapeamento da invasão de espécies de Corbicula (Mollusca, Bivalvia, Veneroida, Corbiculidae) oriundas do sudeste Asiático, na América do Sul. In Água de lastro e bioinvasão (Silva, J.S.V. & Souza, R.C.C.L, orgs) Editora Interciência, Rio de Janeiro, p.39-58.
  • MANSUR, M.C.D. & PEREIRA, D. 2006. Bivalves límnicos da bacia do rio dos Sinos, Rio Grande do Sul, Brasil (Bivalvia, Unionoida, Veneroida e Mytiloida). Rev. Bras. Zool. 23(4): 1123-1147.
  • MANSUR, M.C.D. & PIMPÃO, D.M. 2008. Triplodon chodo, a new species of species of pearly fresh water mussel from Amazon Basin (Mollusca: Bivalvia: Unionoida: Hyriidae). Rev. Bras. Zool. 25(1): 111-115.
  • MANSUR, M.C.D., SANTOS, C.P., PEREIRA, D., PAZ, I.C.P., ZURITA, M.L.L., RODRIGUEZ, M.T.R., NEHRKE, M.V. & BERGONCI, P.E.A. 2012. Moluscos límnicos invasores no Brasil: biologia, prevenção e controle. Redes Editora, Porto Alegre.
  • MARSHALL, W.B. 1917. New and little now species of South American freshwater mussels of the genus Diplodon Proc. U. S. Nat. Mus. 53(2209): 381-388.
  • MARSHALL, W.B. 1922. New pearly freshwater mussels from South America. Proc. U. S. Nat. Mus. 61(16): 1-9.
  • MARSHALL, W.B. 1923. New pearly freshwater mussels from Mexico and Uruguay. Proc. U. S. Nat. Mus. 63(16): 1-4.
  • MARSHALL, W.B. 1926. New land and freshwater mollusks from South America. Proc. U. S. Nat. Mus. 69(12): 1-12.
  • MARSHALL, W.B. 1927. A new genus and two new species of South American fresh-water mussels. Proc. U. S. Nat. Mus. 71(2): 1-4.
  • MASSEMIN, D., LAMY, D., POINTIER, J.P. & GARGOMINY, O. 2010. Coquillages et Escargots de Guyane. 456 pp.
  • MATOS, E. 2007. Ação parasitária em cultivo de moluscos bivalves: um estudo de casa no Nordeste do estado do Pará. In Tópicos em Malacologia – Ecos do XVIII Encontro Brasileiro de Malacologia (Santos, S.B., Pimenta, A.D., Thiengo, S.C., Fernandez, M.A. & Absalão, R.S., orgs.). Technical Books, Rio de Janeiro, p.209-216.
  • MEYER, A.A.N., OLIVEIRA, E. & MARTIM, J. 2010. Classes de comprimento e proporção sexual em Diplodon expansus (Mollusca, Bivalvia, Hyriidae) no rio Piraquara, Paraná, Brasil. Iheringia Ser. Zool. 100(4): 329-335.
  • MEYER, A.A.N., MARTIN, J.K. & OLIVEIRA, E. 2013. Ocorrência e caracterização histológica de marsúpios de Diplodon expansus (Küster, 1856) (Mollusca, Bivalve, Hyriidae) no rio Piraquara, Paraná, Brasil. Biotemas 26(1): 97-108.
  • MEYER, A.A.N., OLIVEIRA, E., TEIXEIRA, T.B. & VIESSER, J.A. 2014. Classes de comprimento e descrição histológica das gônadas de Diplodon ellipticus (Wagner, 1827) (Mollusca, Bivalvia, Hyriidae) em um lago artificial, Morretes, Paraná, Brasil. Biotemas 27(3): 81-96.
  • MIYAHIRA, I.C., SANTOS, S.B., MANSUR, M.C.D. & CARNEIRO, J.B. 2012. Freshwater mussels in Brazil: past, present and future, at least, we hope they have one. American Conchologist 40: 16-18.
  • MIYAHIRA, I.C., MANSUR, M.C.D. & SANTOS, S.B. 2013. Revision of the type specimens of Diplodon ellipticus and Diplodon expansus Spixiana 36: 173-182.
  • MIYAHIRA, I.C., CARNEIRO, J.B., GONÇALVES, I.C.B., LACERDA, L.E.M., OLIVEIRA, J.L., VASCONCELLOS, M.C. & SANTOS, S.B. 2017. Freshwater mollusks and environmental assessment of Guandu River, Rio de Janeiro, Brazil. Biota Neotropica 17(3): http://dx.doi.org/10.1590/1676-0611-BN-2017-0342
    » http://dx.doi.org/10.1590/1676-0611-BN-2017-0342
  • MODELL, H. 1942. Das natürliche system der najaden. Archiv für Molluskenkunde 74(5/6): 161-191. (in German, English translation in Stansberry, D.H. & Soehngen, U. 1964. Sterkiana 14: 1-18).
  • MORRETES, F.L. 1949. Ensaio do catálogo dos moluscos do Brasil. Arq. mus. Paranaense 7: 5-216.
  • NEVES, R.J. 1999. Conservation and commerce: management of freshwater mussel (Bivalvia: Unionoidea) resources in the United States. Malacologia 41(2): 461-474.
  • NEVESSKAJA, L.A. 2009. Principle of systematics and the system of Bivalves. Paleontol. J. 43(1): 1-11.
  • NEWELL, N.D. 1965. The classification of the Bivalvia. Am. Mus. Novit .2206: 1-25.
  • OLAZARRI, J. 1966. Los moluscos de Agua Dulce Del Depto. de Colonia, Uruguay. Part I: Pelecypoda. Comun. Soc. Malacol. Urug. 2(11): 15-37.
  • ORTMANN, A.E. 1911. The anatomical structure of certain exotic naiades compared with that of the North American forms. Nautilus 24: 103-131.
  • ORTMANN, A.E. 1921. South American naiades, a contribution to the knowledge of the fresh-water mussels of South America. Mem. Carnegie Mus. 8(3): 451-670.
  • PARADA, E. & PEREDO, S. 2002. Estado actual de la taxonomía de bivalvos dulceacuícolas chilenos: progresos y conflictos. Rev. Chil. Hist. Nat. 75: 691-701.
  • PARODIZ, J.J. 1968. Annotated catalogue of the genus Diplodon (Unionacea – Hyriidae). Sterkiana 30: 1-22.
  • PARODIZ, J.J. 1969. The tertiary non-marine Mollusca of South America. Ann. Carnegie Mus. 40: 1-242.
  • PARODIZ, J.J. 1973. The species complex of Diplodon delodontus (Lamarck) (Unionacea – Hyriidae). Malacologia 14: 247-270.
  • PARODIZ, J.J. & BONETTO, A.A. 1963. Taxonomy and Zoogeography relationships of the South American naiads (Pelecypoda: Unionacea and Mutelacea). Malacologia 1: 179-213.
  • PEREA, D., SOTO, M., VEROSLAVSKY, G., MARÍNEZ, S. & UBILA, M., 2009. A Late Jurassic fóssil assemblage in Gondwana: biostratigraphy and correlations of the Tacuarembó Formation, Parana Basin, Uruguay. J. S. Am. Earth Sci. 28, 168–179
  • PEREIRA, D., ARRUDA, J.O., MENEGAT, R., PORTO, M.L., SCHWARZBOLD, A. & HARTZ, S.M. 2011. Guildas tróficas, composição e distribuição de espécies de moluscos límnicos no gradiente fluvial de um riacho subtropical brasileiro. Biotemas 24(1): 21-36.
  • PEREIRA, D., MANSUR, M.C.D., DUARTE, L.D.S., OLIVEIRA, A.S., PIMPÃO, D.M., CALLIL, C.T., ITUARTE, C., PARADA, E., PEREDO, S., DARRIGRAN, G., SCARABINO, F., CLAVIJO, C., LARA, G., MIYAHIRA, I.C., RODRIGUEZ, M.T.R. & LASSO, C. 2014. Bivalve distribution in hydrographic regions in South America: historical overview and conservation. Hydrobiologia 735(1): 15-44.
  • PFEIFER, N.T.S. & PITONI, V.L.L. 2003. Análise qualitativa estacional da fauna de moluscos límnicos no Delta do Jacuí, Rio Grande do Sul, Brasil. Biociências 11(2):145-158.
  • PHILIPP, E.E.R. & ABELE, D. 2009. Masters of longevity: lessons from long-lived bivalves – A mini review. Gerontology: 1-11.
  • PIMPÃO, D.M. & MANSUR, M.C.D. 2009. Chave pictórica para identificação dos bivalves do baixo rio Airupuanã, Amazonas, Brasil (Sphaeriidae, Hyriidae e Mycetopodidae). Biota Neotrop. 9: 1-8.
  • PIMPÃO, D.M., MANSUR, M.C.D., BERGONCI, P.E.A. & BEASLEY, C.R. 2012. Comparative morphometry and morphology of glochidial shells of Amazonian Hyriidae (Mollusca: Bivalvia: Unionoida). Am. Malacol. Bull. 30, 73–84.
  • PONDER, W.F. & LINDBERG, D.R. 2008. Phylogeny and evolution of the Mollusca. University of California, California. 469p.
  • QUINTANA, M.G. 1982. Catalogo preliminar de la malacofauna del Paraguay. Rev. Mus. Argent. Cienc. Nat. Bernardino Rivadavia, Zool. 11: 61-158.
  • RAMÍREZ, R., PAREDES, C. & ARENAS, J. 2003. Moluscos del Perú. Rev. Biol. Trop. 51(Suppl. 3): 225-284.
  • RICCI, C.N., COELHO, A.C.S & ALVARENGA, L.C.F. 1988. Diplodon (D.) multistriatus (Lea, 1831): Concha, partes moles e considerações taxonômicas (Mollusca, Bivalvia, Hyriidae). Bol. Mus. Nac. Zool. 325: 1-19.
  • RICCI, C.N., ALVARENGA, L.C.F. & COELHO, A.C.S. 1990. Gloquídios de Diplodon Spix, 1827: D. (D.) multistriatus (Lea, 1831) (Mollusca, Bivalvia, Hyriidae). Bol. Mus. Nac. Zool. 344: 1-10.
  • RUMI, A., GREGORIC, D.E.G., NÚÑEZ, V. & DARRIGRAN, G.A. 2008. Malacologia Latinoamericana - Moluscos de agua dulce de Argentina. Rev. Biol. Trop. 56(1): 77-111.
  • RUPPERT, E.E., FOX, R.S. & BARNES, R.D. 2008. Zoologia dos Invertebrados – Uma abordagem funcional-evolutiva. Editora Roca. São Paulo.
  • SANTOS, S.B., PIMENTA, A.D., THIENGO, S.C., THOMÉ, J.W., ABSALÃO, R.S., MANSUR, M.C.D., VIDIGAL, T.H.D., FERNANDEZ, M.A., TOMÁS, A.R.G., MESQUITA, E.F.M., SALGADO, N.C., MATTHEWS-CASCON, H., MARTINS, I.X., ROCHA-BARREIRA, C. & KAWANO, T. 2009. Mollusca. In Estado da arte e perspectivas para a Zoologia no Brasil (Rocha, R.M. & Boeger, W.A.P., orgs.) Editora UFPR, Curitiba. p.65-90.
  • SANTOS, S.B., MIYAHIRA, I.C., SALGADO, N.C., HEYDRICH, I., PENA, M.S., COLLEY, E., FERNANDEZ, M.A., THIENGO, S.C., GOMES, S.R., SILVA, M.J.M., GONÇALVES, I.C.B., LACERDA, L.E.M., TALLARICO, L.F. & MARTINS, D.S. 2015. Observations on review of the list of endangered continental molluscs of Brazil. Tentacle 23: 26-28.
  • SANTOS-NETO, G.C., BEASLEY, C.R., SCHNEIDER, H., PIMPÃO, D.M., HOEH, W.R., SIMONE, L.R.L. & TAGLIARO, C.H. 2016. Genetic relationships among freshwater mussel species from fifteen Amazonian rivers and inferences on the evolution of the Hyriidae (Mollusca: Bivalvia: Unionoida). Mol. Phylogenet. Evol. 100: 148-159.
  • SCARABINO, F. & MANSUR, M.C.D. 2007. Lista sistematica de los Bivalvia dulciacuícolas viventes de Uruguay. Comun. Soc. Malacol. Urug. 9(90): 89-99.
  • SCHNEIDER, J.A. 2001. Bivalve systematics during the 20th century. J. Paleo. 75(6): 1119-1127.
  • SERRANO, M.A.S., TIETBÖHL, R.S. & MANSUR, M.C.D. 1998. Sobre a ocorrência de moluscos Bivalvia no pantanal de Mato Grosso, Brasil. Biociências 6(1): 131-144.
  • SIMONE, L.R.L. 1994. Anatomical characters and systematics of Anodontites trapesialis (Lamarck, 1819) from South America (Mollusca, Bivalvia, Unionoida, Muteloidea). Stud. Neotrop. Fauna Environ. 29(3): 169-185.
  • SIMONE, L.R.L. 1997. Anatomy and systematics of Anodontites elongatus (Swainson) from Amazon and Paraná basins, Brazil (Mollusca, Bivalvia, Unionoida, Mycetopodidae). Rev. Bras. Zool. 14(4): 877-888.
  • SIMONE, L.R.L. 2006. Land and freshwater molluscs of Brazil. EGB, Fapesp, São Paulo. 390pp.
  • SIMPSON, C.T. 1914. A descriptive catalogue of the Naiades or pearly freshwater mussels. Privately published by Bryant Walker, Michigan.
  • STRAYER, D.L., DOWINING, J.A., HAAG, W.R., KING, T.L., LAYZER, J.B., NEWTON, T.J. & NICHOLS, S.J. 2004. Changing perspectives on pearly mussels, North America’s most imperiled animals. Bioscience 54(5): 429-439.
  • THIELE, J. 1934. Handbuch der systematischen Weichtierkunde – part 3 (Scaphopoda/Bivalvia/Cephalopoda). 779-1022p. (in German, English translation by Bieler, R. & Mikkelsen, P.M. 1998. Handbook of systematic malacology – part 3 and 4. Smithsonian Institution Libraries, Washington D.C. p. 1193-1690).
  • TOMAZELLI, A.C., MARTINELLI, L.A., AVELAR, W.E.P., CAMARGO, P.B., FOSTIER, A., FERRAZ, E.S.B., KRUG, F.J. & JÚNIOR, D.S. 2003. Biomonitoring of Pb and Cd in two impacted watersheds in southeast Brazil, using the freshwater mussel Anodontites trapesialis (Lamarck, 1819) (Bivalvia: Mycetopodidae) as a biological monitor. Braz. Arch. Biol. Technol. 46(4): 673-684.
  • WÄCHTLER, K., MANSUR, M.C.D., RICHTER, T. 2001. Larval type e early postlarval biology in Naiads (Unionoida). In Ecology e Evolution of the Freshwater Mussels Unionoida (Bauer G, Wächtler K., eds.). Springer-Verlag, Berlim. 93-125p.
  • WHELAN, N.V., GENEVA, A.J. & GRAF, D.L. 2011. Molecular phylogenetics analysis of tropical freshwater mussels (Mollusca: Bivalvia: Unionoida) resolves the position of Coelatura and supports a monophyletic Unionidae. Mol. Phylogenet. Evol. 61(2): 504-514.
  • VAUGHN, C.C. 2017. Ecosystem services provided by freshwater mussels. Hydrobiologia. DOI 10.1007/s10750-017-3139-x
    » https://doi.org/10.1007/s10750-017-3139-x
  • VAZ J.F., MANTEGAZZA, E., TELES, H.M.S., LEITE S.P.S. & MORAIS, L.V.C. 1987. Levantamento planorbídico do Estado de São Paulo (Brasil): 4a Região Administrativa. Rev. Saúde Públ. S. Paulo 21: 371-379.
  • VEITENHEIMER-MENDES, I.L. 1973a. Contribuição ao estudo do gênero Leila Gray, 1840 (Mycetopodidae: Bivalvia). Iheringia, Ser. Zool. 62(42): 64-89.
  • VEITENHEIMER-MENDES, I.L. 1973b. Anodontites Bruguière, 1792 no Guaíba - RS (Mycetopodidae: Bivalvia). I – Anodontites trapesialias forbesianus (Lea, 1860). Iheringia, Ser. Zool. 62(44): 32-49.
  • VEINTENHEIMER-MENDES, I.L. & MANSUR, M.C.D. 1978a. Mycetopoda legumen: Lasídio e desenvolvimento parasitário (Bivalvia: Mycetopodidae). Rev. Bras. Biol. 38(3): 531-536.
  • VEINTENHEIMER-MENDES, I.L. & MANSUR, M.C.D. 1978b. Morfologia, histologia e ecologia de Mycetopoda legumen (Martens, 1888) (Bivalvia: Mycetopodidae). Iheringia, Ser. Zool. 67(52): 33-71.
  • VEINTENHEIMER-MENDES, I.L. & MANSUR, M.C.D. 1979. Redescrição de Mycetopoda legumen (Martens, 1888)(Bivalvia: Mycetopodidae). Rev. Bras. Biol. 39(3): 695-702.
  • VERNHOUT, J.H. 1914. The non-marine molluscs of Surinam. I. Notes Leyden Mus. 36: 1-46.
  • XU, M., DARRIGRAN, G., WANG, Z., ZHAO, N., LIN, CH & PAN, B. 2015. Experimental study on control of Limnoperna fortunei biofouling in water transfer tunnels. Journal of Hydro-environment Research 9(2): 248-258.
  • ZANARDINI, I.F. 1965. Nota sôbre Diplodon e Anodontites (Mollusca-Pelecypoda) de rios de Curitiba (Paraná). Bol. Inst. Def. Patrim. Nat. Zool. 6: 1-11.

Publication Dates

  • Publication in this collection
    2017

History

  • Received
    14 Mar 2017
  • Reviewed
    30 Aug 2017
  • Accepted
    17 Nov 2017
Instituto Virtual da Biodiversidade | BIOTA - FAPESP Departamento de Biologia Vegetal - Instituto de Biologia, UNICAMP CP 6109, 13083-970 - Campinas/SP, Tel.: (+55 19) 3521-6166, Fax: (+55 19) 3521-6168 - Campinas - SP - Brazil
E-mail: contato@biotaneotropica.org.br