Austrolebias queguay (Cyprinodontiformes, Rivulidae), a new species of annual killifish endemic to the lower Uruguay river basin

Wilson S Serra,Marcelo Loureiro

doi:10.3897/zse.94.29115

Abstract

In this article we describe a new species of the annual fish genusAustrolebiasfrom the lower Uruguay river basin. The fusion of the urogenital papilla to the first anal fin ray in males and the pigmentation pattern, indicates a close relationship with the clade formed byA.bellottii,A.melanoorus, andA.univentripinnis. The new species can be differentiated from those by the following combination of characters: presence of well-defined light bands contrasting with the sides of the body, the distal portion of the anal fin dark gray, pelvic fins dark bluish green and bases united at about 50–80% on their medial margins, pectoral fins with iridescent blue sub-marginal band, and general coloration of body bluish green. The new species can only be found in wetlands of the Queguay river, an area included in the Uruguayan protected areas system and represents so far the only annual fish species endemic to the lower Uruguay river basin.

Highlights

In this article we describe a new species of Austrolebias from wetlands of the Queguay river, that shares similar morphological traits to the clade formed by A. bellottii, A. melanoorus, and A. univentripinnis
It differs from A. bellottii and A. univentripinnis by the presence of well-defined light blue bands contrasting with the sides of the body in adult males (Fig. 2); from A. melanoorus, by the presence of dark gray coloration of the distal portion of the anal fin in males, pelvic-fins dark bluish green and bases united at about 50–80% on their medial margins, pectoral-fins with iridescent blue sub-marginal band, and general coloration of the body bluish green
The new species described in this article presents all diagnostic characters for the genus Austrolebias proposed by Costa (2006): absence of scales between corner of mouth and anterior portion of preopercular region and ventral portion of opercular region, deep urohyal, dark gray to black infraorbital bar and supraorbital spot, dorsal and anal fins rounded in males, long urogenital papilla in male, and reduced ventral process of angulo-articular

Summary

Introduction

Austrolebias, one of the most specious annual fish genus in the family Rivulidae, is composed of 47 valid species and is distributed in Bolivia, Paraguay, southern Brazil, northeast Argentina, and Uruguay, in the La Plata, Patos-Merin, and southwestern Amazon basins (Alonso et al 2018, Calviño et al 2016, Costa, 2006, 2014, Costa et al 2017, García et al 2012, Loureiro et al 2011, Nielsen and Pillet 2015, Volcan et al 2014, 2017). 1 in Costa 2006), diagnosed by chromatic characters; and an unnamed clade that lacks morphological diagnostic characters This clade is composed of A. bellottii (Steindachner), A. vandenbergi (Huber), A. apaii Costa (all from La Plata basin), A. melanoorus (Amato) (from La Plata and Patos Merin basins), and A. univentripinnis Costa and Cheffe (from Patos Merin basin). Afterwards, based on another morphological phylogeny, Costa (2010) added A. patriciae to the “A. bellottii” species group. In this article we describe a new species of Austrolebias from wetlands of the Queguay river (lower Uruguay river basin), that shares similar morphological traits to the clade formed by A. bellottii, A. melanoorus, and A. univentripinnis

Materials and methods

Findings

Discussion