Density-dependent regulatory mechanisms of the generative potency in the males of a bank vole Myodes glareolus

Morphological analysis revealed destructive changes in the testicular tissue of bank volesMyodes glareolus Schreber, 1780 during different phases of a population fluctuation. The most pronounced changes were observed at the peak phase, when karyolysis of the Leydig cells and degeneration of spermatogenous cells were recorded in 90% of males. During the increase phase, depression of androgenous testicular function was observed in only 50% of males and atrophy of seminiferous tubules in 30% of males. During the low phase, the proportion of males with destructive changes in generative and endocrine portions of the testicles did not exceed 30%. Morphometrical analysis of spermatozoa demonstrated that the size of the head and nucleus were related to the phase of the population fluctuation. Lengths of the middle and main parts of the spermatozoon tail, as well as the size of the acrosome, were not related to phase of the population fluctuation.