Morphological characteristics of the spotted thicklip loach Triplophysa strauchii (Nemacheilidae) from the Uba River (upper Irtysh basin)

Abstract

The spotted thicklip loach is a Central Asian fish species native to many water bodies of Kazakhstan. This species belongs to a complex taxonomic group of fish, the genus Triplophysa. Three subspecies of the spotted thicklip loach are known for water bodies of Kazakhstan: T. s. strauchii, T. s. ruzskyi, and T. s. zaisanicus, but their taxonomic status and distribution require clarification. The modern distribution of the spotted thicklip loach is very wide; it inhabits the basins of Balkhash-Alakol, Tarim, the Chu and Syr Darya rivers, and is also known for the basin of Lake Zaysan. Currently, this species expands its range far to the north, where it has successfully acclimatized in the endorheic rivers and lakes of Central and Northern Kazakhstan. In 2016, the spotted thicklip loach was discovered in the Uba River of the upper Irtysh basin. Here we present a description of the external morphology, including coloration, plastic and meristic features, body proportions, fin shape, lip structure, features of the intestine, and swim bladder. Features of sexual dimorphism were also investigated. Characteristic features of Triplophysa strauchii have been revealed. In order to clarify the range of this species, further research is needed in the Irtysh basin.