Morphological, Ecological, and Genetic Characteristics of the Sandy Sculpin (Leocottus kesslerii, Cottidae) from Lake Baikal and Arakhlei and Gusinoe Lakes (Transbaikalia)

Local forms of the sandy sculpin (Leocottus kesslerii (Dybowski 1874)), formed in Lake Baikal and Arakhlei and Gusinoe lakes, were studied. The studies demonstrated the existence of differences between the lake forms according to the following traits of external morphology. In the Baikal form, the head width is greater than the length; in the Arakhlei and Gusinoe forms, the head width is less than its length. In the Baikal and Gusinoe forms, there is a gap between the dorsal fins; it is absent in the Arakhlei form, in which the dorsal fins come into contact with each other. In the Arakhlei form, the anal fin is long (37.4–43.0%, on average, 39.3% SL); in the Baikal form, the A base length reaches 29.0–34.5% (on average, 32.9% SL). In the Baikal and Arakhlei forms, there are small and sparse bone prickleson the body; they are large and dense in the Gusinoe form. The detected differences demonstrate a low level of morphological isolation of the forms. More significant differences are demonstrated by the ecological indices: growth rate, nutrition spectra, peculiarities of reproduction, and absolute fecundity values. Differences in ecological indices are caused by the adaptation of the sandy sculpin forms to the specific conditions of the lakes in which they live. The study of genetic differentiation was carried out by the control region of mtDNA. The sandy sculpin forms had a weak genetic isolation. The average p-distances between the L. kesslerii forms varied from 0.33 ± 0.12 to 0.51 ± 0.24%. These values of the genetic distances are within the limits of intraspecific variability. The data obtained on the morphological, ecological, and genetic differentiation of the lake forms of the sandy sculpin demonstrated that fish from Lake Baikal and Arakhlei and Gusinoe lakes belong to the nominative subspecies Leocottus kesslerii kesslerii.