Leukocyte blood composition of Emys orbicularis and Mauremys capsica (Reptilia: Testudines: Emydidae, Geoemydidae) at syntopy

Abstract

Data on the leukocyte blood composition of two co-habiting species of freshwater turtles, Emys orbicularis and Mauremys caspica, from the Republic of Dagestan (Russia) are provided. 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 (λWilks = 0.459, p < 0.001), sex (λWilks = 0.809, p = 0.019) and their interaction (λWilks < 0.001, 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 in specific environmental conditions. On the other hand, the blood formula (WBC) showed the possibility of an active response, more pronounced in M. caspica than in E. orbicularis.

Immunity in Sea Turtles: Review of a Host-Pathogen Arms Race Millions of Years in the Running

“…For example, fibropapillomatosis (FP) is a tumorous disease that affects sea turtles. The dramatic increase in FP prevalence since the 1980s is attributed to a virus, and an unknown environmental factor thought to be anthropogenic in nature [68][69][70]. Results from genomic [71], proteomic [72][73][74] and transcriptomic studies [70,75,76] have consistently identified immune genes as dysregulated between healthy and diseased turtles or by levels of exposure to marine contaminants [73].…”

“…The dramatic increase in FP prevalence since the 1980s is attributed to a virus, and an unknown environmental factor thought to be anthropogenic in nature [68][69][70]. Results from genomic [71], proteomic [72][73][74] and transcriptomic studies [70,75,76] have consistently identified immune genes as dysregulated between healthy and diseased turtles or by levels of exposure to marine contaminants [73]. Additionally, sea turtles are possible reservoirs for zoonotic viruses, as C. mydas, along with snakes and pangolins, have been suggested as potential intermediate hosts of SARS-CoV-2 [77].…”

“…Multidisciplinary interest in sea turtle immunology is growing, guided by ecoimmunology and 'One Health' principles, and the application of omics techniques, protein isolation, and purification, microscopy, and histology will aid in the characterization of immune components [65,67,85]. The adaption, standardization, and application of these techniques to sea turtle research will continue to identify dysregulated and diseaserelated pathways, allowing the selection of potential precision medicine treatments [70,85]. However, the turtle immune response is influenced by individual and species-specific factors, including season, sex, and temperature [19,33,86,87].…”