Osteology of the viscerocranium of the lake minnow Rhynchocypris percnurus (Leuciscidae) from Northern and Central Kazakhstan

Abstract

The article is devoted to the osteology of the lake minnow - an indigenous representative of the ichthyofauna of Kazakhstan. This species has a wide range in northern Eurasia and a debatable taxonomic structure. The generic status of the lake minnow has changed several times - currently it is often assigned to the genus Rhynchocypris. Within this species, several subspecies have been described, two of which live in the water bodies of Northern and Central Kazakhstan. Modern information on the lake minnow from the Northern Kazakhstan is limited to morphometric data, on the basis of which it is assigned to the nominative subspecies R. p. percnurus. Another form, previously described as a subspecies of R. czekanowskii from Northern Kazakhstan, was subsequently considered as a subspecies of the lake minnow R. p. ignatowi, which also inhabits the water bodies of Central Kazakhstan. Its systematic status remains unclear, and available data on morphology and distribution are scarce.

The purpose of this study was to identify the characteristic features and interpopulation variability of the visceral skull bones of the lake minnow from the water bodies of Northern and Central Kazakhstan. The research material consisted of fish from populations of the Kylshakty River (Northern Kazakhstan) and the Karkaraly River (Central Kazakhstan). Using the method of preparing and staining skeletons, osteological preparations of fish from both populations were obtained. As a result of the analysis of osteological characteristics, the bones of the viscerocranium of the lake minnow from the water bodies of Kazakhstan were characterized in detail for the first time.  Characteristic features of the shape of the maxillary, dentary, opercular, basihyal and pharyngeal bones were revealed. Interpopulation differences concern the shape of the basihyal and the third epibranchial, as well as the presence or absence of the first pharyngobranchial. The data obtained may indicate the morphological distinctiveness of the populations of Northern and Central Kazakhstan.