Spermatid Morphology Within the Germinal Epithelium of the Southern Bunchgrass Lizard, Sceloporus aeneus

Indianapolis, IN

Ultrastructural data on spermatid characters during spermiogenesis are on the increase for reptiles, but are still relatively limited within squamates. A recent study compared Sceloporus bicanthalis to S. variabilis and found 8 character differences between these species that reside in the same genus. This study focuses on the events of spermiogenesis within an oviparous and seasonal mating lizard, Sceloporus aeneus. This lizard is the sister taxon to S. bicanthalis and thus we explored the question: do sibling species within a genus show differences in the ontogeny of spermiogenesis? Five lizards were collected in April 2012 from Toluca, Mexico. The testicular tissues were processed normally for TEM and analyzed to access the ultrastructural spermatid changes occurring during spermiogenesis. The present data were compared to the spermiogenic information available on the viviparous lizard, Sceloporus bicanthalis. Interestingly, few differences exist between S. bicanthalis and S. aeneus. Degrading and coiled myelin figures were visible within the developing acrosome, which are likely remnants of transport vesicles from the Golgi complex. Acrosome and subacrosome granules are present during early spermiogenesis. During late spermiogenesis, an electron lucent line, the acrosome lucent ridge, between the subacrosomal space and the acrosomal medulla was observed in S. aeneus spermatids, which has been mentioned in other squamates but not accurately described. Our study suggests that spermiogenesis may be more conserved in sibling taxa within a genus. The significance of these findings is not known as too few lizards with the same genus and across taxa have been studied to date.