COMPARATIVE MORPHOLOGICAL CHARACTERISTICS OF THE ARAL ROACH, RUTILUS ARALENSIS (CYPRINIFORMES: LEUCISCIDAE), FROM THE SYR DARYA RIVER BASIN, UZBEKISTAN

This article presents the external morphology, the variability of morphometric characters and a comparative analysis of the Aral roach, Rutilus aralensis, from water bodies of the Syr Darya River basin: the Syr Darya River and lakes Arnasay and Yallama. A total of 72 specimens collected in 2022–2026 were examined for 7 meristic and 24 plastic characters following Pravdin (1966). Meristic characters showed low variability (CV < 10%) and remained within the species norm in all samples. The populations of the Syr Darya River and Lake Arnasay differed significantly (P ≤ 0.05) in head and snout length, predorsal and postdorsal distances, caudal peduncle length, body depth, eye diameter, interorbital width and postorbital distance, whereas the Lake Yallama population occupied an intermediate position between them. The differences revealed reflect the phenotypic plasticity of the species under the contrasting conditions of riverine and lacustrine habitats.