Sexual maturation in common vole (Microtus arvalis) males raised under laboratory conditions

The common vole is one ofthe most numerous rodents in Europe and Asia but its reproductive biology is not fully described. It is thought that females reach reproductive abilities at a very young age, however, there is no data concerning male sexual maturation. The aim of the present study was to determine the rate of sexual maturation of males of the common vole. Research was carried out on 4, 6, 8 and 10 week-old animals. Body, testes and accessory sex glands weights were compared to evaluate morphological development. Epididymal sperm quality was assessed by a motility test, sperm tail membrane integrity, viability, maturity and sperm head morphology. Moreover, the number of sperm cells in 1 mm3 of semen was evaluated. The largest body weights were observed in 8 and 10 week-old males, which also possessed the highest relative weights of gonads and accessory sex glands. These groups of males produce about 2 times more gametes than 6 week-old individuals. The highest seamen quality was noted in 8 and 10 week-old males. Based on the obtained results, it is concluded that among the investigated age groups the most appropriate male age for fertile copulation is between 8 and 10 weeks.