Leukocytic Indices and Micronucleus in Erythrocytes as Population Markers of the Immune Status of Pelophylax ridibundus (Pallas, 1771) (Amphibia: Ranidae) Living in Various Biotopic Conditions

Abstract

Abstract—A differentiated assessment of blood cells and types of micronuclei in the erythrocytes of marsh frogs (Pelophylax ridibundus) living in reservoirs of the Nizhny Novgorod region was performed. The water reservoirs differ by origin, morphology, and chemical composition. The specific abiotic conditions (a peat bog) and anthropogenic load resulted in the most pronounced change in the leukocyte differential count, corresponding to the neutrophilic type of leukemoid reaction, and in an increased micronucleus fraction in the erythrocytes. A moderate positive correlation between the increase in the number of disintegrated micronuclei and the content (mg/L) of nitrites in the reservoir was found (r = 0.72, p = 0.0179). The complex action of high concentrations of technogenic chemical pollutants (copper, chromium, and oil products) caused the activation of erythropoiesis and humoral immunity, which was confirmed by the nature of the leukemoid reaction of a lymphatic type. The cellular and humoral types of immune reaction aimed at self–foreign molecule differentiation provided stability of the frog ontogenesis under anthropogenic pressure. Integral leukocyte indexes, such as the blood cell indicator, the neutrophil–lymphocyte ratio, the lymphocyte–granulocyte index, and the index of leukocyte shift, which reflect the level of the body’s general reactivity, can be considered as population markers of the immune status of amphibians.