Description of Vipera berus nikolskii Vedmederja, Grubant et Rudaeva pholidosis in the Middle Don’s basin

Background. Pholidosis – the location of the scutes on the body of reptiles – is used for taxonomic, as well as for determination of an influence of environmental factors on ontogenesis. We described the features of pholidosis of Nikolsky’s viper in the Middle Don basin and compared the features of males and females. Materials and methods. In the Middle Don basin, material was collected in the Bobrovsky, Novousmansky, Anninsky, and Borisoglebsky districts of Voronezh Region. The average values of the of pholidosis features for males and females were counted, a comparison of these features between males and females in the Voronezh region, as well as a comparison with vipers from other regions were done. A scalation of the pileus of reptiles, e.g. variations of each type of scutellum, and combination of scutes were described. Results. Sex differences were described for Vipera berus nikolskii on the territory of Voronezh region: females have a larger number of abdominal, nasolabial and posterior nasal scutes, while males have pairs of sub-caudal scales. Significant interpopulation differences in the number of abdominal scutes were revealed between vipers from Voronezh Region and the environs of Samara, Nizhny Novgorod, Volgograd, Ivanovo Regions, and the Republic of Mari El. In all cases, the number of abdominal plates of vipers from the territory of Voronezh Region is significantly higher. The authors identified 77 variations in the scutellum of the pileus, these variations were combined into five groups. Conclusions. A sexual dimorphism found out in the research was probably associated with similar sex differences in the metric characters: females have a longer body and head length compared to males, and males have a longer tail. One of the most stable features of the pholidosis is the number of abdominal scutes, and this trait is convenient for identifying interpopulation differences. The scaling of the pileus is highly variable. The most variable feature is the number of frontal scutes. Among the pileus groups, the most common is the group 1 (typical location of the scutes)