New small-sized species of Astyanax (Characiformes: Characidae) from the upper rio Paraguai basin, Brazil, with discussion on its generic allocation

A new species of Astyanax is described from the rio Salobra, tributary of rio Cuiabá, rio Paraguai basin. The new taxon can be distinguished from its congeners by having a well-defined dark midlateral stripe on body extending from the posterior margin of the opercle to the base of middle caudal-fin rays and a single vertical elongate humeral blotch. Although the new species is described in Astyanax, some specimens present an incomplete or a discontinuous series of perforated scales in the lateral line. Therefore, a discussion on its generic allocation is presented. Comments on different patterns of coloration among dark-striped species of Astyanax are also provided. The discovery of a new species in an underwater tourist point relatively near a large urban center underscores that even fish species daily observed by hundreds of people in limpid waters may lack a formal taxonomic identity. Such finding also highlights how the megadiverse Brazilian freshwater ichthyofauna still needs efforts and investments to identify and describe new taxa.

Keywords:
Lateral line; Nobres; Longitudinal stripe; Taxonomy; Tourist destination

Authorship

Fernando C. P. Dagosta

Faculdade de Ciências Biológicas e Ambientais, Universidade Federal da Grande Dourados, Rodovia Dourados/Itahum, km 12, 79804-970 Dourados, MS, Brazil. (FCPD) ferdagosta@gmail.com (corresponding author).Universidade Federal da Grande DouradosBrazilDourados, MS, BrazilFaculdade de Ciências Biológicas e Ambientais, Universidade Federal da Grande Dourados, Rodovia Dourados/Itahum, km 12, 79804-970 Dourados, MS, Brazil. (FCPD) ferdagosta@gmail.com (corresponding author).

http://orcid.org/0000-0001-7163-296X

Manoela M. F. Marinho

Departamento de Sistemática e Ecologia, Universidade Federal da Paraíba, Cidade Universitária, s/n, Castelo Branco, 58051-900 João Pessoa, PB, Brazil. (MMFM) manoela.marinho@gmail.com.Universidade Federal da ParaíbaBrazilJoão Pessoa, PB, BrazilDepartamento de Sistemática e Ecologia, Universidade Federal da Paraíba, Cidade Universitária, s/n, Castelo Branco, 58051-900 João Pessoa, PB, Brazil. (MMFM) manoela.marinho@gmail.com.

http://orcid.org/0000-0003-4226-666X

Edited-by

Marcelo Melo

Correspondence

Fernando C. P. Dagosta ferdagosta@gmail.com

Author's Contribution

Fernando Cesar Paiva Dagosta: Conceptualization, Data curation, Formal analysis, Funding acquisition, Investigation, Methodology, Project administration, Resources, Software, Supervision, Validation, Visualization, Writing-original draft, Writing-review and editing.

Manoela Maria Ferreira Marinho: Conceptualization, Data curation, Formal analysis, Funding acquisition, Investigation, Methodology, Project administration, Resources, Supervision, Validation, Visualization, Writing-original draft, Writing-review and editing.

Competing Interests

The authors declare no competing interests.

Ethical Statement

Type series was collected under Instituto Brasileiro do Meio Ambiente e dos Recursos Naturais Renováveis (IBAMA License number 37815/1).

SCIMAGO INSTITUTIONS RANKINGS

Figures | Tables

Figures (7)
Tables (1)

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FIGURE 1 |
Holotype of Astyanax nobre, MZUSP 125905, 25.6 mm SL, Brazil, Mato Grosso State, Municipality of Nobres, rio Paraguai basin, upper rio Salobra drainage.

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FIGURE 2 |
Lateral view of right side, premaxillary, maxillary, and dentary of Astyanax nobre, MZUSP 118302, paratype. Scale bar = 0.5 mm.

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FIGURE 3 |
Live coloration of Astyanax nobre, paratypes, MZUSP 118302: A. Male; B. Female. Specimens not measured. Photo by W. Ohara.

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FIGURE 4 |
Underwater photographs of wild specimens of Astyanax nobre at its type locality Recanto Ecológico Lagoa Azul, Bom Jardim district, Municipality of Nobres, Mato Grosso State, rio Salobra drainage, rio Paraguai basin: A. Pair of males; B. Pair of females. Details about differences between sexes can be found in Sexual dimorphism section. Photo by M. Melo.

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FIGURE 5 |
Distribution map of Astyanax nobre in the rio Salobra, upper rio Paraguai basin, Brazil. Brown star (type locality).

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FIGURE 6 |
Type locality of Astyanax nobre, rio Salobra at Lago Azul, tributary of rio Cuiabá, rio Paraguai basin, 14º35’43.2”S 55º58’09.6”W, Nobres, Mato Grosso State, Brazil. Photo by M. A. Junghans.

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FIGURE 7 |
Different types of dark midlateral stripes in Astyanax: A. Stripe of variously shapes and pigmentation starting posterior to the humeral blotch and never connected to it (e.g., A. bagual and A. eremus); B. Stripe starting immediately posterior to the humeral blotch and usually ending at the tip of middle caudal-fin rays (e.g., species typically assigned to the Astyanax bimaculatus-group); C. Narrower stripe starting at posterior margin of the opercle, becoming blurred posteriorly and not reaching the caudal fin (e.g., Jupiaba anterior and J. ajuricaba); D. Stripe starting immediately posterior to the opercle (e.g., A. joaovitori and A. scintillans). See discussion for further details. Fish layout modified from Van der Sleen, Albert (2018)Van der Sleen P, Albert JS, editors. Field Guide to the fishes of the Amazon, Orinoco & Guianas. Princeton: Princeton University Press; 2018..

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TABLE 1 |
Morphometric data of Astyanax nobre. Range includes the holotype and 30 paratypes. SD = Standard deviation.

FIGURE 1 | Holotype of Astyanax nobre, MZUSP 125905, 25.6 mm SL, Brazil, Mato Grosso State, Municipality of Nobres, rio Paraguai basin, upper rio Salobra drainage.

FIGURE 2 | Lateral view of right side, premaxillary, maxillary, and dentary of Astyanax nobre, MZUSP 118302, paratype. Scale bar = 0.5 mm.

FIGURE 3 | Live coloration of Astyanax nobre, paratypes, MZUSP 118302: A. Male; B. Female. Specimens not measured. Photo by W. Ohara.

FIGURE 4 | Underwater photographs of wild specimens of Astyanax nobre at its type locality Recanto Ecológico Lagoa Azul, Bom Jardim district, Municipality of Nobres, Mato Grosso State, rio Salobra drainage, rio Paraguai basin: A. Pair of males; B. Pair of females. Details about differences between sexes can be found in Sexual dimorphism section. Photo by M. Melo.

FIGURE 5 | Distribution map of Astyanax nobre in the rio Salobra, upper rio Paraguai basin, Brazil. Brown star (type locality).

FIGURE 6 | Type locality of Astyanax nobre, rio Salobra at Lago Azul, tributary of rio Cuiabá, rio Paraguai basin, 14º35’43.2”S 55º58’09.6”W, Nobres, Mato Grosso State, Brazil. Photo by M. A. Junghans.

FIGURE 7 | Different types of dark midlateral stripes in Astyanax: A. Stripe of variously shapes and pigmentation starting posterior to the humeral blotch and never connected to it (e.g., A. bagual and A. eremus); B. Stripe starting immediately posterior to the humeral blotch and usually ending at the tip of middle caudal-fin rays (e.g., species typically assigned to the Astyanax bimaculatus-group); C. Narrower stripe starting at posterior margin of the opercle, becoming blurred posteriorly and not reaching the caudal fin (e.g., Jupiaba anterior and J. ajuricaba); D. Stripe starting immediately posterior to the opercle (e.g., A. joaovitori and A. scintillans). See discussion for further details. Fish layout modified from Van der Sleen, Albert (2018)Van der Sleen P, Albert JS, editors. Field Guide to the fishes of the Amazon, Orinoco & Guianas. Princeton: Princeton University Press; 2018..

TABLE 1 | Morphometric data of Astyanax nobre. Range includes the holotype and 30 paratypes. SD = Standard deviation.

	Holotype	Range	Mean	SD
Standard length (mm)	25.6	21.6–30.2	23.8	–
Percentages of standard length
Depth at dorsal-fin origin	31.3	25–32	29.3	2.0
Snout to dorsal-fin origin	52.0	51.6–56.8	53.3	1.1
Snout to pectoral-fin origin	27.3	26.8–31	27.9	0.9
Snout to pelvic-fin origin	48.8	46.3–52.6	49.3	1.4
Snout to anal-fin origin	62.9	61.3–68	63.6	1.4
Caudal-peduncle depth	10.9	8.6–11	9.8	0.6
Caudal-peduncle length	10.9	9.6–13.4	11.4	1.0
Pectoral-fin length	21.5	19.7–23.3	21.8	0.9
Pelvic-fin length	16.0	14.7–18.7	16.4	0.9
Dorsal-fin length	27.0	25.2–31.1	27.4	1.3
Dorsal-fin base length	15.6	12.2–15.6	14.3	0.8
Anal-fin length	18.4	17.5–21	18.9	0.8
Anal-fin base length	27.3	23.6–28.2	26.3	1.2
Eye to dorsal-fin origin	38.3	36.6–41.4	38.5	1.1
Dorsal-fin origin to caudal-fin base	52.0	45.4–52.2	48.9	1.6
Head length	27.7	25.1–29.5	27.5	0.9
Percentages of standard length
Horizontal eye diameter	42.3	40–45.2	42.9	1.3
Snout length	23.9	22.7–30.6	25.3	1.7
Interorbital width	36.6	31.5–38.7	34.5	1.6
Upper jaw length	53.5	45.3–53.5	49.5	2.1

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Sociedade Brasileira de Ictiologia Neotropical Ichthyology, Núcleo de Pesquisas em Limnologia, Ictiologia e Aquicultura, Universidade Estadual de Maringá., Av. Colombo, 5790, 87020-900, Phone number: +55 44-3011-4632 - Maringá - PR - Brazil
E-mail: neoichth@nupelia.uem.br

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New small-sized species of Astyanax (Characiformes: Characidae) from the upper rio Paraguai basin, Brazil, with discussion on its generic allocation

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[1] Edited-by

Marcelo Melo