An endangered new species of seasonal killifish of the genus <i>Austrolebias</i> (Cyprinodontiformes: Aplocheiloidei) from the Bermejo river basin in the Western Chacoan region

Abstract

<i>Austrolebias wichi</i>, new species, is herein described from seasonal ponds of the Bermejo river basin in the Western Chacoan district in northwestern Argentina. This species was found in a single pond, a paleochannel of the Bermejo River, which is seriously disturbed by soybean plantations surrounding it. Despite intensive sampling in the area, this species was only registered in this pond where it was relatively scarce. Therefore, we consider this species as critically endangered. This species is the sister species of <i>A. patriciae</i> in our phylogenetic analyses and is similar, in a general external aspect, to <i>A. varzeae</i> and <i>A. carvalhoi</i>. It can be distinguished among the species of <i>Austrolebias</i> by its unique color pattern in males. Additionally, from <i>A. varzeae</i> by presenting a supraorbital band equal or longer than the infraorbital band (vs. shorter) and from <i>A. patriciae</i> by the convex dorsal profile of head (vs. concave). Further diagnostic characters and additional comments on its ecology and reproduction are provided.