Postgraduate Student,

All-Russian Scientific and Research Institute of Agricultural Afforestation,

Russian Academy of Agrarian Sciences

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Abstract. The article deals with the variability of indicators of water snake pholidosis in populations of Volga Akhtubinsk and Don flood-plains. The article shows that the number of plates on snake’s body is quite steady. The limits of variability of these features in the studied populations are slightly wider, than the species limits mentioned in literature. The author makes distinctions in the

nature of variability of bilateral structures. The number of the first row temporal plates is stable, while the combination of the supralabial, postorbital and preorbital is more varied. The combination of the second row temporal and lower-labial plates is mostly varied; they are characterized by the highest level of polymerization. The indicators of pholidosis are distinguished by variability degree: the lowerand supralabial plates variability is minimal (to 10 %), the preorbital and 2nd row temporal plates variability is maximal (from 24 to 36 %).

The different elements of pholidosis reveal varying degrees of fluctuating asymmetry: high rates of asymmetry are specific for the second row temporal plates, minimal rates are specific for the supralabial ones. The article reveals the interpopulation distinctions in pholidosis features. In the population of the Don flood-plain the range of bilateral structures variability is wider; in the population of the Volga and Akhtubinsk flood-plains the coefficient of asymmetry is higher. It testifies to the bigger destabilization of the process of water snake ontogenesis in the Volga Akhtubinsk flood-plains.

Key words: water snake, Natrix tessellata, meristic features, pholidosis, Volgograd region, asymmetry.