Adaptive Reactions of the Blood System of Elaphe dione , Natrix natrix , and N. tessellata (Reptilia: Colubridae)

—A comparative interspecific assessment of the leukocyte profile of young Elaphe dione , Natrix natrix , and N. tessellata is given. Juvenile snakes were obtained in captivity from females captured, while pregnant, from Volga populations. Eosinophils and basophils predominated in the blood of young E. dione , and the total content of mononuclear cells (agranulocytes) was lower compared to the young of N. tessellata and N. natrix . At the same time, the species of the genus Natrix differed in the content of all three types of mononuclear cells; namely, the proportion of azurophils and monocytes was higher in N. tessellata and that of lymphocytes was higher in N. natrix. The main contribution to the balance of mononuclear cells was made by lymphocytes. The leukocyte composition of young snakes had no pronounced lymphocytic profile, the contribution of the specific reactivity of the organism to the overall adaptive response of the body of young snakes to environmental conditions was small. According to the content of lymphocytes, the studied species were arranged in descending order in the following series: N. natrix ( Me 60.00, IQR 2.50) → N. tessellata (52.00, 6.00) → E. dione (40.00, 5.00). The increased value of the leukocyte shift index in E. dione young testified to the predominant role of granulocytes in the immune response with some lag of lymphocyte–monocyte cells and later activation of the effector link of the immune response (lymphocytes) compared with young of N. natrix and N. tessellate. While the specific reaction of the immune system decreased, a compensator activation of the nonspecific protective blood system was observed in the organism of E. dione. The increase in the content of granulocytes in the blood of young snakes was a characteristic indicator of an increase in environmental stress, assessed by the integral leukocyte index (the ratio of heterophiles and lymphocytes). The integral leukocyte indices reflected an imbalance of the adaptive response of the blood system in young snakes kept in captivity in relation to adult males and females from natural populations.