Seasonal variations cause morphological changes and altered spermatogenesis in the testes of viscacha (Lagostomus maximus)

Abstract

This study complements the previous investigations of the reproductive biology of maleviscachas, a rodent of a seasonal Hystricognathi that exhibits photoperiod-induced morpho-logical variations in the reproductive system. In the present study, a quantitative analysis ofspermatogenesis was performed during the summer and the spring. Spermatogonial cellswere analyzed to determine by immunolabelling for STRA8 and DAZL, which are essentialfor spermatogenesis. Six free-living male viscachas were captured, three animals in thesummer during the period of reproductive activity and three animals in the spring duringthe period of testicular regression. The testes of the viscachas were collected and processedfor light microscopy, macroscopic and immunochemical analyses. The germ and Sertolicells present in the seminiferous tubules were quantitatively analyzed in each animal. Theefficiency coefficient for spermatogonial mitosis, meiotic yield, overall spermatogenesisyield and Sertoli cell index, revealed that the Sertoli cells in male viscachas captured duringthe summer had a reduced capacity to structurally and nutritionally support the develop-ing round spermatids compared with the male viscachas captured during the spring. Theanimals produced less sperm during the spring than the summer, suggesting a seasonalimpact on spermatogenesis. Immunolabelling for STRA8 and DAZL was detected duringsummer and spring seasons. These results suggest that in seasonal rodents, such as themale viscachas, the photoperiod promotes significant changes in the testis and in the germcell yield.