Yermolenko S. Ecologicalcharacteristics of snakes of the genus Natrix in the conditions of the Steppe Dnieperarea

Objects oftheresearchare individuals and populations of N. natrix and N. tessellata of the steppe Dnieper valley. A subject of the research are population characteristics of grass and dice snakes: population density, spatial structure, sexual structure; morphological features of N. tessellata; morphophysiological indexes, helminth communities of N. natrix and N. tessellata, content of heavy metals in liver, kidneys and bones of the dice snake. The research objective is determining the state of populations of Natrixspecies in the conditions of the steppe Dnieper area. The method of full helminthautopsywas applied to study of the snakes’ helminth fauna. The revealed helminths were calculated and photographed by the 3.5 megapixels camera for further identifying. Helminths were fixed and stored in 70% ethanol. For identification of snakes’ feeding effectiveness,we counted the Fulton’s coefficient of fatness, which is depended with a linear size and weight of snakes. Accounting of snakes and their populations’ sexual structure carried out by the tested methods during the spring-summer and summer-autumn periods at the same routes. The abundance was investigated by a line transect method. The width of transect depended on size of the water body bank andvegetation density. For a research of content of heavy metals (zinc, copper, lead and cadmium) in snake bodies (liver, kidneysand bones). The level of metalswas determinedby atomic-adsorptive spectrophotometry. The research of morphometric and morphological features of snakespopulations was conducted by standard techniques. The morphophysiological and fatness indices of N. natrix and N. tessellata from the habitats being under different intensity of anthropogenic impact were studied. The population of dice snakes from anthropogenically transformed biotopes of the Sanitary Protection Zone of Prydniprovska Thermal Power Plant has higher indices of the heart and lung than snakes from populations inhabited the near-natural ecosystems. It was also revealed that with an increase in the anthropogenic load, the relative weight of the grass snake’s liver increases. The formation of infra-and component communities of helminths of both snakespecies in different ecosystems of the steppe Dnieper region is analysed. We also estimate the possibility of using the biodiversity indices of the helminth communities for assessing the state of zoocoenoses in general. The changes in the helminth biodiversity indices indirectly indicate the degradation of the animal community structure. Possibly, it can serve as a biomarker for the state of aquatic and semiaquatic ecosystems. It was revealed that in the specific species composition of the snake helminthofauna of the steppe Dnieper area the proportion of the number of allogenic species decreases in the communities. The possibility of using dice snakes as bioindicator species for assessment of the environmental pollution by heavy metals is considered. It has been established that in the dice snakes from the ecosystems adjacent to PrydniprovskaTPP, the content of cadmium, zinc and lead in the liver and kidneys 1.5–2.1 times higher than the content of these metals in the organs of the snakes from the near-natural low-transformed ecosystems. In addition, snakes from anthropogenically transformed biotopes have the increased level of copper in the kidneys (almost 1.4 times) and the zinc in bones (by 1.3 times).