The Leukocyte Blood Composition of Emys orbicularis and Mauremys caspica (Reptilia: Testudines: Emydidae, Geoemydidae) at Syntopy

—Data on the leukocyte blood composition of two cohabiting species of freshwater turtles, Emys orbicularis and Mauremys caspica , from the Republic of Dagestan (Russia). Lymphocytes are the predominant cells in the blood of females and males of both species. Heterophils predominated among granulocytes. Two-way multivariate analysis of variance showed a statistical significance of the influence of two factors on the leukocyte formula of freshwater turtles, namely, species (λ Wilks = 0.459, p < 0.001), sex (λ Wilks = 0.809, p = 0.019), and their interaction (λ Wilks < 0.000001, p < 0.001). The blood formula (WBC) of E. orbicularis females showed higher levels of eosinophils ( z = 3.040, p = 0.001) and basophils ( z = 5.394, p < 0.001) and reduced levels of heterophils ( z = 3.579, p < 0.001) and lymphocytes ( z = 3.391, p < 0.001) compared to M. caspica females. Males of E. orbicularis differed from those of M. caspica by increased levels of eosinophils ( z = 2.716, p = 0.003) and basophils ( z = 4.829, p < 0.001) and a reduced level of heterophils ( z = 3.474, p < 0.001). With general adaptive responses, interspecific differences were clearly expressed: the variability in the parameters of the white blood cell system of E. orbicularis was associated with rearrangement of the ratio of granulocyte cells (heterophils, eosinophils, and basophils). The predominance of a specific component of the immune system (lymphocytes) was found in the immune responses of M. caspica. Changes in the leukocyte profiles of freshwater turtles were associated with a change in the agranulocyte–granulocyte ratio, which was confirmed by statistically significant differences in the integral leukocyte indices. The leukocyte profile of Emys orbicularis testified to the insufficient resource of adaptive mechanisms under specific environmental conditions. On the other hand, the blood formula (WBC) and body reactivity indices of the two species showed the possibility of an active response, which was more pronounced in M. caspica than in E. orbicularis.