Pimelodus microstoma Steindachner, 1877, a valid species of pimelodid catfish (Siluriformes: Pimelodidae) from the upper rio Paraná drainage

Abstracts

Pimelodus microstoma, which has been treated as a junior synonym of P. fur, is resurrected and its type locality restricted to Irisanga (=Orissanga), São Paulo State, in the upper rio Paraná. An identification key is provided for Pimelodus species from the upper portions of the Paraná drainage.

Natterer; Geographic distribution; Type-locality; Pimelodus fur


Pimelodus microstoma, espécie que tem sido tratada como sinônimo júnior de P. fur, é revalidada e sua localidade-tipo restringida para Irisanga (=Orissanga), Estado de São Paulo, alto rio Paraná. Uma chave de identificação das espécies de Pimelodus da porção superior do rio Paraná é fornecida.


SCIENTIFIC NOTE

Pimelodus microstoma Steindachner, 1877, a valid species of pimelodid catfish (Siluriformes: Pimelodidae) from the upper rio Paraná drainage

Frank Raynner V. RibeiroI; Carlos Alberto S. de LucenaII

IUniversidade do Estado do Pará – Núcleo de Santarém, Av. Plácido de Castro, 1399, 68040-090, Santarém, PA, Brazil. fraynner@hotmail.com

IILaboratório de Ictiologia, Museu de Ciências e Tecnologia, Pontifícia Universidade Católica do Rio Grande do Sul, Av. Ipiranga, 6681, 90619-900 Porto Alegre, RS, Brazil. lucena@pucrs.br

ABSTRACT

Pimelodus microstoma, which has been treated as a junior synonym of P. fur, is resurrected and its type locality restricted to Irisanga (=Orissanga), São Paulo State, in the upper rio Paraná. An identification key is provided for Pimelodus species from the upper portions of the Paraná drainage.

Key words: Natterer, Geographic distribution, Type-locality, Pimelodus fur.

RESUMO

Pimelodus microstoma, espécie que tem sido tratada como sinônimo júnior de P. fur, é revalidada e sua localidade-tipo restringida para Irisanga (=Orissanga), Estado de São Paulo, alto rio Paraná. Uma chave de identificação das espécies de Pimelodus da porção superior do rio Paraná é fornecida.

Pimelodus microstoma Steindachner, 1877 is one of the 24 species of the paraphyletic Neotropical genus Pimelodus (Lundberg & Littmann, 2003). Eigenmann & Eigenmann (1888, 1890) were not able to demonstrate the validity and distinctiveness between P. microstoma and P. fur (Lütken, 1874) (type locality: Rio das Velhas [rio São Francisco basin]). Thus, subsequent authors (e.g. Gosline, 1945, Fowler, 1951) treated P. microstoma as a junior synonym of P. fur, a species known from the São Francisco basin.

Pimelodus microstoma was described based on three specimens collected by the Austrian naturalist Johann Natterer, who conducted many collection expeditions in Brazil from 1818 to 1835. Some Pimelodus specimens collected by Natterer were initially treated as P. maculatus La Cépède, 1803 by Kner (1858), until Steindachner (1877) recognized them as representatives of an undescribed species which he formally named P. microstoma. Steindachner (1877) was aware that specimens came from Natterer's collections and referred to the type locality as "Brazil, von Irisanga [=Orissanga, São Paulo], Rio Branco und Barra do Rio Negro." The occurrence of such a wide distribution (Amazon and Paraná basins) is unlikely for a Pimelodus species.

The examination of the type series of P. microstoma demonstrated that all syntypes are co-specific, and its comparison with the type series and/or specimens of Pimelodus species from the Amazon drainage, allowed its recognition as a valid and distinct species. Pimelodus microstoma is distinguished from all Amazonian Pimelodus species, and from recently described Pimelodus species from rio São Francisco (Ribeiro & Lucena, 2003), by the combination of the following characters: a deep, robust body; relatively long adipose fin, occupying at least half of the distance between the end of the dorsal-fin base and the beginning of the caudal peduncle; prominent upper jaw, allowing the visualization of nearly the whole premaxillary tooth plate; small mouth and a short maxillary barbel, usually not reaching the base of the caudal peduncle; and a gray uniform color pattern with only a few dark dots (sometimes very weak or absent) in the antero-lateral region.

The only Amazonian species with a gray color pattern is P. blochii (Valenciennes, 1840). However, the results of principal components analysis (PCA) corroborate the discrimination between P. microstoma and P. blochii. Plots of the second and third principal components revealed the complete separation of the two species (Fig. 1). Character loadings that most strongly contributed to discrimination along PC axes are: distance between dorsal-fin base end and adipose-fin origin (0.33), distance between urogenital papilla and anal-fin base origin (0.30), adipose-fin length (0.26), adipose-fin depth (-0.37), interorbital width (-0.26), and pectoral spine length (-0.25) on second PC axis, and distance between end of dorsal-fin base and adipose-fin origin (0.54), interorbital width (0.27), anterior internarial width (0.23), adipose-fin length (-0.51), adipose-fin depth (-0.28), and internarial length (-0.21) on the third axis.

Johann Natterer's journey in Brazil included many Brazilian states other than Amazonas: São Paulo, Paraná, Minas Gerais, Goiás, Mato Grosso, and Pará (Papavero, 1971). Therefore, it is possible that syntypes of P. microstoma were captured in the drainages of the rios São Francisco, Paraguay and Paraná. The comparison between these syntypes with Pimelodus specimens from the aforementioned drainages showed many differences, mainly color pattern ones. In the next paragraphs, we discuss the diagnostic characters of P. microstoma that warrant its validity and distinctiveness from its congeners inhabiting the rio Paraná and neighboring drainages.

Although Natterer himself did not collect specimens in the rio São Francisco drainage, Dr. J. E. Pohl, one of the scientists who joined Natterer in Brazil to form the Austrian Mission – collected around the cities of Pirapora and Barra do Rio das Velhas (currently Guaicu), both in the rio São Francisco basin (Papavero, 1971). Pohl's collections arrived in Vienna in four consignment contents, which included 42 fish specimens among other zoological groups (Riedl-Dorn, 1999).

Pimelodus microstoma and P. fur are quite similar but differ in the number of gill rakers (17-22 [19-20 in syntypes of P. microstoma] vs. 16-18, respectively) and width of interorbital space (19.0-26.5% of HL [22.4-22.6% of HL in the syntypes of P. microstoma] vs. 12.1-14.9% of HL, respectively). Pimelodus microstoma differs from P. maculatus (from the rio São Francisco basin) by the number of gill rakers (17-22 vs. 25-28, respectively) and by predorsal length (37.1-40.8% of SL [37.5-38.8 % of SL in the syntypes] vs. 43.2-45.8% of SL, respectively), besides several other morphometric parameters.

The results of principal components analysis (PCA) revealed a complete separation between P. microstoma, P. fur and P. maculatus along the second and third principal components (Fig. 2). With 5.2 % of total variation of the data, PC2 contains the main shape differences between species. Character loadings strongly contributing to discrimination along PC axes are: adipose-fin length (0.36), distance between urogenital papilla and anal-fin base origin (0.32), caudal peduncle length (0.30), interorbital width (-0.41), mouth width (-0.37) and supraoccipital process width (-0.30) on the second PC axis; and internarial length (0.48), internarial posterior width (0.37), adipose-fin length (0.26), distance between dorsal-fin base end and adipose-fin origin (-0.53), supraoccipital process width (-0.26) and horizontal eye diameter (-0.16) on the third axis.

It is important to point out that a specimen from Juazeiro, Bahia (MZUSP 24723) was found to be very similar to P. microstoma. Despite the large number of specimens examined from the rio São Francisco drainage, only this specimen possessed the color pattern typical of P. microstoma. We prefer to regard it provisionally as Pimelodus sp., since a more encompassing analysis is beyond the scope of this work.

Eight species were originally described or cited for the drainages of the rio Paraguay or lower rio Paraná (including the rio Iguaçu): Pimelodus maculatus, P. albicans (Valenciennes, 1840), P. argenteus Perugia, 1891, P. brevis Marini, Nichols & La Monte, 1933, P. ortmanni Haseman, 1911, P. absconditus Azpelicueta, 1995, P. mysteriosus Azpelicueta, 1998, and P. atrobrunneus Vidal & Lucena, 1999. Pimelodus maculatus has a spotted body (vs. gray or few spots restricted to the antero-dorsal region of the body in P. microstoma). Like P. microstoma, Pimelodus albicans has teeth on the vomer but can be distinguished by the longer maxillary barbels, reaching the middle of anal fin, and a uniform brownish color pattern or, according to Eigenmann & Eigenmann (1890), by three dark longitudinal stripes in young specimens. Pimelodus brevis has a short body, smaller eye (6.4 vs. 3.7-3.8 times in HL) and does not exhibit dots on the body flanks (the holotype is missing, and thus comparative analysis was according to Marini et al., 1933). Pimelodus ortmanni has comparatively longer dots, forming 3-5 rows on the lateral surface of the body, and on fins. Pimelodus absconditus has thick and fleshy, well-developed lips. Pimelodus mysteriosus has spots in three or four rows along the body and a very long maxillary barbel, reaching the tip of caudal-fin lobes. Pimelodus argenteus and P. atrobrunneus do not have a spotted body.

Three species were originally described for the upper rio Paraná – P. paranaensis Britski & Langeani, 1988, P. heraldoi Azpelicueta, 2001, and P. platicirris Borodin 1927. Pimelodus microstoma can also be distinguished from these species by the same combination of characters cited above. Pimelodus heraldoi has dots arranged irregularly on the body, forming 8-9 rows. Pimelodus platicirris has 3-5 rows of dots on lateral surface of the body and dorsal and caudal fins. Pimelodus paranaensis has very small dots on the body sides and a premaxillary tooth plate with pointed postero-lateral corners (vs. rounded in P. microstoma).

During survey analyses of Pimelodus specimens housed in the fish collection of MZUSP, the senior author concluded that some upper rio Paraná specimens (see Material Examined) are very similar to the syntypes of P. microstoma (see Morris & Sabaj, 2006 for images of the syntype NMW 45824.1) regarding morphometrics, meristics, and chromatic features (Fig. 3). Therefore, we assigned these specimens the species name P. microstoma and restricted its type locality to Orissanga, São Paulo State, upper rio Paraná basin (thereby removing the species from the list of the fishes of the rio Amazonas drainage). Below we provide a provisional key to Pimelodus species from the upper rio Paraná.

Acknowledgments

We are grateful to the following people: Osvaldo Oyakawa and José Figueiredo (MZUSP) for the support given to the first author during the examination of the collection and for the loan of Pimelodus specimens; Helmut Wellendorf (NMW) for the loan of the syntypes of P. microstoma and for taking photographs; and John Lundberg (ANSP) for data and photographs of pimelodids. The All Catfish Species Inventory Project supported the visit of FRVR to MZUSP. The manuscript was improved by suggestions from Paulo Lucinda. Photograph in Fig. 3 was taken by José P. Silva (MCP). John Lundberg and an anonymous reviewer provided important suggestions in the manuscript.

Literature cited

Received September 2006

Accepted December 2006

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Publication Dates

  • Publication in this collection
    10 July 2007
  • Date of issue
    Mar 2007

History

  • Received
    Sept 2006
  • Accepted
    Dec 2006
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