title: 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 male viscachas, a rodent of a seasonal Hystricognathi that exhibits photoperiod-induced morphological variations in the reproductive system. In the present study, a quantitative analysis of spermatogenesis was performed during the summer and the spring. Spermatogonial cells were analyzed to determine by immunolabelling for STRA8 and DAZL, which are essential for spermatogenesis. Six free-living male viscachas were captured, three animals in the summer during the period of reproductive activity and three animals in the spring during the period of testicular regression. The testes of the viscachas were collected and processed for light microscopy, macroscopic and immunochemical analyses. The germ and Sertoli cells present in the seminiferous tubules were quantitatively analyzed in each animal. The efficiency coefficient for spermatogonial mitosis, meiotic yield, overall spermatogenesis yield and Sertoli cell index, revealed that the Sertoli cells in male viscachas captured during the summer had a reduced capacity to structurally and nutritionally support the developing round spermatids compared with the male viscachas captured during the spring. The animals produced less sperm during the spring than the summer, suggesting a seasonal impact on spermatogenesis. Immunolabelling for STRA8 and DAZL was detected during summer and spring seasons. These results suggest that in seasonal rodents, such as the male viscachas, the photoperiod promotes significant changes in the testis and in the germ cell yield.
authors: Department of Surgery, Faculty of Veterinary Medicine and Animal Science, University of São Paulo, São Paulo, Brazil.
authors: Naira Caroline
authors: NC
authors: Godoy Pieri
authors: Department of Surgery, Faculty of Veterinary Medicine and Animal Science, University of São Paulo, São Paulo, Brazil.
authors: Paulo Ramos
authors: PR
authors: da Silva Santos
authors: Department of Surgery, Faculty of Veterinary Medicine and Animal Science, University of São Paulo, São Paulo, Brazil.
authors: Kelly Cristine
authors: KC
authors: Santos Roballo
authors: School of Veterinary Sciences, National University of La Plata, La Plata, Provincia de Buenos Aires, Argentina.
authors: Mirta Alicia
authors: MA
authors: Flamini
authors: School of Veterinary Sciences, National University of La Plata, La Plata, Provincia de Buenos Aires, Argentina.
authors: Claudio Gustavo
authors: CG
authors: Barbeito
authors: Department of Veterinary Medicine, Faculty of Animal Science and Food Engineering, University of São Paulo, Pirassununga, São Paulo, Brazil; Department of Surgery, Faculty of Veterinary Medicine and Animal Science, University of São Paulo, São Paulo, Brazil.
authors: Carlos Eduardo
authors: CE
authors: Ambrosio
authors: Department of Surgery, Faculty of Veterinary Medicine and Animal Science, University of São Paulo, São Paulo, Brazil.
authors: Maria Angélica
authors: MA
authors: Miglino
authors: Department of Veterinary Medicine, Faculty of Animal Science and Food Engineering, University of São Paulo, Pirassununga, São Paulo, Brazil. Electronic address: daniele@usp.br.
authors: Daniele
authors: D
authors: Dos Santos Martins
mesh_terms: D000818:Animals; D008297:Male; D012377:Rodentia / Q000502:physiology*; D012621:Seasons; D013091:Spermatogenesis / Q000502:physiology*; D013737:Testis / Q000502:physiology*
keywords: Hystricomorpha; Photoperiod; Reproduction cycle; Rodent