Rapid Morphological Diversification of the Cyprinid Fish Oreoleuciscus potanini (Cyprinidae) in the Course of Formation of a Reservoir in a River of the Semiarid Zone.

The analysis of phenetic diversity in Potanin Altai osman Oreoleuciscuspotanini from the Taishir Reservoir built in 2007 on the Zavkhan River (Great Lakes Hollow, Mongolia), revealed four morphologically discernible forms. Earlier, there were described two forms of O. potanini from the riverine part of the Zavkhan River and three forms in the lakes of the Great Lakes Hollow. The data of the study demonstrate similarity with cyclic morphogenesis in the closely related species Oreoleuciscushumilis in the Lakes Valley also belonging to the Central Asian closed basin.

The first case of morphological differentiation of Altai Osman Oreoleuciscus potanini (Cyprinidae, Actinopterigii) in a river.

The variability of osteological characters has been investigated in cyprinid fish of the genus Oreoleuciscus (Potanin Altai osman) from the river Zavkhan; this fish species is endemic for water bodies of Central Asia. Multivariate analysis of 13 quantitative parameters of the size of the cerebral and visceral skull and the pectoral girdle and the construction of ontogenetic channels allowed the detection of morphologically distinct forms in the fluvial habitats. The result obtained provides additional proof of the possibility of sympatric diversification of fish in river ecosystems. One of the two fluvial forms discovered has been shown to be identical (with regard to the osteological characters) to a previously described herbivorous form of O. potanini from the standing water bodies of the Great Lakes Hollow (Western Mongolia).

[HELMINTHS OF THE COMMON ROACH (RUTILUS RUTILUS LINNAEUS, 1758) AND THE EUROPEAN PERCH (PERCA FLUVIALITIS LINNAEUS, 1758) IN THE LAKE TERKHIIN TSAGAAN (MONGOLIA)].

The article provides data about helminthes of the common roach and the European perch in the Lake Terkhiin Tsagaan (Mongolia). Six parasite species were found. Data on the occurrence of the trematode species and larvae of Streptocara crassicauda are obtained for the first time. Species composition of Diplostomum spp. metacercariae parasitizing in fish eyes is updated.