Major Regularities of Transformation of the Small Mammal Ovaries in Unfavourable Environmental Conditions: Ecological and Morphological Aspects

Abstract

The aim of the study was to determine the patterns of structural and functional organization of the ovaries of female small mammals inhabiting technogenically altered ecosystems.Material and methods. We studied the ovaries of small mammal species belonging to the insectivore and rodent families (common shrew, field and pygmy wood mice, common and bank voles, mole vole, steppe pied) that live in anthropogenically altered ecosystems (zones of influence of ferrous and nonferrous metallurgy, as well as gas processing factory). The resulting material was processed using observational histological, histochemical, immunohistochemical and morphometric tests.Results. The results obtained demonstrated that in technogenically altered ecosystems the intensified reproduction results in a complex of morphofunctional reactive and adaptive changes in the ovaries of females of the studied species. The size of the ovaries was reduced; the area of the cortical substance was reduced. In the cortex, there was revealed a decrease in the number of follicles varying over a wide range - from a moderate decrease to their almost complete absence. There was found a decrease in the area of the vessels of the microvasculature; this was one of the major reasons for the increased follicular atresia. In follicles of various types, there was an increase in the proportion of cells expressing the proapoptotic protein P53. A decrease in the number of follicles resulted in the connective tissue overgrowth. The presence of cysts lined with epithelium of various heights was revealed in the cortex and medulla. Conclusion. The results obtained evidence that in technogenically altered ecosystems a decreased ovarian reserve is observed in the ovaries of female small mammals; it is associated with a more rapid depletion of the follicle reserve in the cortex due to both - intensification of reproduction and more rapid death of follicles in unfavourable environmental conditions.