title: Spermatogenesis in the grey squirrel (Sciurus carolinensis) and changes during sexual regression.
abstract: In the testes of sexually active grey squirrels 8 stages of spermatogenesis were recognized each with a characteristic association of germ cells. The low numbers of spermatozoa in squirrel testes are the result of fewer spermatogonial divisions compared with those of most other mammals as well as a low efficiency of spermatogenesis, with only 42% of the germ cells becoming spermatozoa. A period of testicular regression which may be prolonged follows the breeding season in June/July. In fully regressed testes no stages of spermatogenesis could be recognized, the lumen of the seminiferous tubules was occluded and no stages later than primary spermatocytes were seen.
mesh_terms: D000818:Animals; D002452:Cell Count; D008297:Male; D012589:Sciuridae / Q000502:physiology*; D012671:Seminiferous Tubules / Q000166:cytology; D012708:Sertoli Cells / Q000166:cytology; D013076:Sperm Count; D013091:Spermatogenesis; D013094:Spermatozoa / Q000502:physiology; D013737:Testis / Q000033:anatomy & histology / Q000502:physiology*