Redescription of Corydoras undulatus Regan, 1912 (Siluriformes: Callichthyidae), with comments on the identity of Corydoras latus Pearson, 1924.

Alessandra Bono,Felipe Alonso,Pablo Lehmann A,Luiz Fernando Caserta Tencatt,Zuogang Peng

doi:10.1371/journal.pone.0211352

Abstract

A redescription of Corydoras undulatus Regan, 1912 is presented. The original description of C. undulatus is very succinct, as is its diagnosis, which is based only on external morphology. Additional information in the scientific literature on this species is scarce. Specimens from the distribution area of this species were analyzed; Paraná and Paraguay river basins in Argentina, Uruguay river basin in Argentina, Brazil and Uruguay, and the Laguna dos Patos system in Brazil. Morphological analysis, principal component analysis (PCA), meristic comparison and osteological description were performed. Corydoras undulatus can be distinguished from its congeners mainly by having the following combination of characters: mesethmoid short, with anterior tip short, smaller than 50% of the entire bone length; posterior margin of the pectoral-fin spine with nearly all serrations directed towards origin of spine; pectoral-fin spine with conical serrations; and its peculiar color pattern. The analysis of the material from the different basins did not indicate relevant morphological differences, suggesting that the species presents a wide distribution in La Plata and Laguna dos Patos drainages. The shared geographic distribution between these two systems is also present in other fish species. The current work presents data about the type locality, taxonomy, osteology, distribution and ontogenetic variation of color pattern in C. undulatus. Comments on the identity of a very similar congener, Corydoras latus, will also be provided.

Highlights

Corydoras Lacepède, 1803 comprises the majority of species of the Corydoradinae, and represents the genus with the greatest species-rich among the Siluriformes
Whereas the original description of Corydoras undulatus contains limited information on morphological characters and, mainly, osteological characters, having been based on only three specimens; here we provide a redescription of C. undulatus, detailing its geographic distribution area, Laguna dos Patos system, Parana, Uruguay and Paraguay basins
Corydoras undulatus can be distinguished from its congeners, with exception of C. bilineatus, C. elegans, C. gracilis, C. guapore, C. latus, C. mamore, C. nanus, C. napoensis Nijssen & Isbrucker, 1986, C. nijsseni, and C. paucerna, by having the following combination of features: mesethmoid short, with anterior tip short, smaller than 50% of entire bone length; posterior margin of pectoral-fin spine with most serrations directed towards origin of spine; pectoral-fin spine with conical serrations

Summary

Introduction

Corydoras Lacepède, 1803 comprises the majority of species of the Corydoradinae, and represents the genus with the greatest species-rich among the Siluriformes. Nijssen & Isbrucker [4] present a review of the Corydoras listing the measurements and counts of the 115 species analyzed. In this work, these authors reformulated the groupings originally proposed by Nijssen [3], reducing them from nine to five. Corydoras undulatus was included into the "Corydoras elegans-group" with seven other species: C. elegans Steindachner, 1877 (Amazon River at Tefe, Amazonas, Brazil); C. hastatus Eigenmann & Eigenmann, 1888 (Villa Bella [= Parintins, 2 ̊38’S 56 ̊45’W], Amazonas, Brazil); C. latus Pearson, 1924 (Lagoons, Lago Rojoagua [Rogoagua], Rıo Beni basin, Upper Amazon system, Beni, Bolivia); C. guapore Knaack, 1961 (main stream of upper Rio Guapore, Rondonia, Brazil); C. pygmaeus Knaack, 1966 (near Calama, 8 ̊05’S 62 ̊52’W, along Rio Madeira near mouth of Rio Jipirana [= Machado River], Rondonia State, Brazil); C. nanus Nijssen & Isbrucker, 1967 (little tributaries of Gran-Rio between Ligoria [= Ligolio] and Awaradam Falls, Brokopondo, Suriname); C. gracilis Nijssen & Isbrucker, 1976 (Rio Jauna [= River Juma] at Trans-Amazonica highway, about 6 ̊09’S, 59 ̊55’W, tributary of Rio Aripuaña, Amazonas, Brazil [corrected locality])

Methods

Results

Conclusion