Morphological, ecological and genetic characteristics of the sandy sculpin (<i>Leocottus kesslerii</i>, Cottidae) from the lakes Baikal, Arakhlei and Gusinoe, Transbaikalia

Studies on local forms of the Sandy sculpin, Leocottus kesslerii, in the lakes Baikal, Arakhlei and Gusinoye show that the differences between lake forms in terms of external morphology lie in the head length to width ratio. In the Baikal form, the head is wider than long, vs the opposite in both Apakhlei and Gusinoe forms. In the Baikal and Gusinoe forms, there is a gap between the dorsal fins, a gap being absent from the Arakhlei form and the dorsal fins are in touch with each other. In the Arakhlei form, the anal fin is long (37.4–43%, on average 39.3% SL). In the Baikal form, the length of the A base reaches 32.9% SL (29.0–34.5%). In the Baikal and Arakhlei forms, small and sparse bone prickles are present on the body, these being large and dense in the Gusinoe form. The differences identified show a low level of morphological isolation of the forms. More significant differences are established in ecological features: growth rate, food spectrum, reproductive characteristics, and fecundity values. The differences in ecological features are due to the adaptation of the Sandy sculpin forms to specific conditions of the lakes they inhabit. Studies on genetic differentiation were carried out using the control region (CR) of mtDNA. The study forms of the Sandy sculpin revealed weak genetic isolation. The p-distances between the L. kesslerii forms averaged from 0.33 ± 0.12 to 0.51 ± 0.24%. Such low values of genetic distances clearly lie within the limits of intraspecific variability. The data obtained on the morphological, ecological and genetic differentiation of lake forms of the Sandy sculpin show that fish from the lakes Baikal, Arakhlei and Gusinoe belong to the same nominative subspecies, Leocottus kesslerii kesslerii.