Ecological and physiological analysis of immune reactions of Pelophylax ridibundus and P. lessonae (Amphibia: Ranidae) in anthropogeneously transformed territories

Abstract

The purpose of the work is to assess the state of Anura populations living in an anthropo-genic territory according to a set of indicators of the body’s immune homeostasis. The objects of the study were Pelophylax ridibundus (Pallas, 1771) and P. lessonae (Camerano, 1882), living in the natural populations of reservoirs in Nizhny Novgorod. Priority chemical pollutants of the water bodies were determined by spectrophotometry. Species were identified using a multiplex PCR test system. The identification results were confirmed by sequencing of the mitochondrial ND2 gene and a fragment of the SAI protein. We counted the numbers of erythrocytes and leukocytes, determined the leukocyte profile and the level of immune complexes in all frogs. An excess of the water quality standard for the content of heavy metals was revealed in all the water bodies. Molecular genetic diagnostics showed the presence of both “pure” P. ridibundus and individuals with introgressive mtDNA of the Anatolian form of the lake frog (P. cf. bedriagae) in the sample of lake frogs. In the sample of pond frogs, all studied individuals had only species-specific mt- and nDNA markers of P. lessonae. P. ridibundus differed from P. lessonae by an increased content of erythrocytes, neutrophils, basophils, small immune complexes, and a reduced content of lymphocytes. The revealed changes in the immunohematological parameters of green frogs were caused by the complex henotoxic effect of pollutants in the water bodies. A decrease in the lymphocytes/eosinophils ratio index was shown with an increase in the concentration of nitrites, an increased activity of humoral immune responses in conditions of sulfate pollution of the aquatic environment, an increase in the proportion of myelocytes in the blood of frogs with an increased concentration of manganese and nitrates in water. Under conditions of environmental stress, the blood regulatory systems of frogs reflected a stress-induced reaction, which was more pronounced in the body of lake frogs compared to pond ones.