Stage and season effects on cell cycle and apoptotic activities of germ cells and Sertoli cells during spermatogenesis in the spiny dogfish (Squalus acanthias)

L M McClusky
2005 Reproduction  
To understand the processes involved in the spatial and temporal maturation of testicular cells in Squalus acanthias, we used standard morphometry, proliferating-cell nuclear antigen (PCNA) and terminal deoxynucleotidyl transferase-mediated dUTP nick end-labelling (TUNEL) immunohistochemistry. Except for immature spermatocysts (germinal zone, GZ; early-stage pre-meiotic, E-PrM), the number of cysts in all subsequent stages and the total number of cysts in the spermatogenic progression varied
more » ... sonally. The spermatogenic cycle spans about 2 years and is interrupted by germcell clone deletion via apoptosis at the mitosis–meiosis transition in April/May, manifesting as a zone of degeneration (ZD). Rate of displacement of the ZD across the testis diameter indicates that late-stage premeiotic (L-PrM) generations 12–13 require 9–10 months to reach the mature-spermatid stage. Also, the number of cysts completing spermatogenesis is approximately 4–5-fold less than the number that entered spermatogenesis proper 2 years earlier. Pronounced gonocytogenesis in the germinal ridge was coincident with ZD formation in April/May, but it was absent in the fall when mature spermatogonial and meiotic activities had resumed. Whereas strong Sertoli cell PCNA immunoreactivity dominated the GZ cyst cell-cycle activities throughout the year, except during the spring/summer months, the spermatogonial- and Sertoli-cell PCNA indices in E-PrM cysts were inversely related. PCNA immunoreactivity in spermatocytes was seasonal and dependent on the stage of meiosis. TUNEL labelling was limited to spermatogonia and increased stage-dependently in the PrM region (L-PrM = mid-stage PrM ≫E-PrM ≫GZ), correlating with ZD formation, in a season-dependent manner. Results imply that effects of normal regulatory factors in Squalus are stage- and process-specific.
doi:10.1530/rep.1.00177 pmid:15615901 fatcat:7msgi2gji5gffa56xi5owuk3ly