Population-ecological aspects of adaptive reactions of the Emys orbicularis (Reptilia: Emydidae) blood system during invasion

We carried out the assessment of the leukocyte profile of the blood and the analysis of infection with hemoparasites of the European swamp turtle Emys orbicularis (Linnaeus, 1758) of the Astrakhan oblast of Russia. In the dynamics of two-year observations in the leukocyte profiles of the European swamp turtle, we noted an increase in the relative content of heterophiles (males) and a decrease in the proportion of monocytes (males, females), an increase in the leukocyte shift index (males, females), a decrease in the lymphocyte-granulocyte index (males). These results illustrate a decrease in the immune response in general and the dominant role of granulocytes in nonspecific adaptive reactions of the organism. The proportion of affected erythrocytes, the extent and intensity of invasion of Haemogregarina spp. in females increased, in males it remained at the same level. Gender differences in morphometric parameters of infected red blood cells of turtles were revealed. The area of red blood cells of males significantly exceeded that of females, but did not change in comparison with infected cells. The affected erythrocytes of females differed by a larger area and had a modified shape. In the blood of infected individuals, the ratio of leukocyte cells changed in favor of granulocytes with a decrease in the number of agranulocytes. A positive relationship was revealed between the indicators of invasion and the content of eosinophils in the peripheral blood of turtles, as well as a negative relationship with the integral leukocyte indices of the ratio of lymphocytes and heterophiles to eosinophils. The totality of the values of the integral leukocyte indices reflected the influence of the parasite, in which the reactivity of the host organism did not exceed the normal values. The revealed positive moderate correlation between the intensity of invasion and the length of the swamp turtle's carapace makes it possible to predict a higher intensity of infection during the ontogenetic development of reptiles.