Ultrastructure of the reproductive system of the black swamp snake (Seminatrix pygaea). V. The temporal germ cell development strategy of the testis

Abstract

AbstractThe germ cell development strategy during spermatogenesis was investigated in the black swamp snake (Seminatrix pygaea). Testicular tissues were collected, embedded in plastic, sectioned by ultramicrotome, and stained with methylene blue and basic fuchsin. Black swamp snakes have a postnuptial pattern of development, where spermatogenesis occurs from May to July and spermiation is completed by October. Though spatial relationships are seen between germ cells within the seminiferous epithelium during specific months, accumulation of spermatogonia and spermatocytes early in spermatogenesis and the depletion of spermatocytes and accumulation of spermatids late in spermatogenesis prevent consistent cellular associations. This temporal germ cell development within an amniotic testis is consistent with that seen in other recently studied temperate reptiles (slider turtle and wall lizard). These reptiles’ temporal development is more similar to the developmental strategy found in anamniotes than the spatial germ cell development that characterizes birds and mammals. Our findings also imply that a third germ cell development strategy may exist in temperate breeding reptiles. Because of the phylogenetic position of reptiles between anamniotes and other terrestrial amniotes, this common germ cell development strategy shared by temperate reptiles representing different orders may have significant implications as far as the evolution of sperm development within vertebrates.