The Fine Structure of Spermatids During Spermiogenesis Within the Sea Snake, Pelamis platurus

Indianapolis, IN

Little is known about spermatid ontogeny during spermiogenesis in snakes, as there are only two complete studies in ophidians that detail the spermatid ultrastructure within Cottonmouths and Copperheads. Therefore, the focus of the following research is to expand our understanding of the developmental steps of spermiogenesis in snakes by studying spermatids in Pelamis platurus caught in Costa Rica in 2010. The testes were removed and the tissues were processed with standard electron microscopy. The spermatids of P. platurus share many similar ultrastructural characteristics to what has been described for other squamates. Two notable differences between the spermatids of P. platurus and those of other snakes is a more prominent central lacuna within the nucleus and radiating arrays of longitudinal manchette microtubules. The P. platurus epinuclear lucent zone is shorter in comparison to other squamates and may be a synapomorphy for snakes. Also, the midpiece is much longer and is similar to that reported for all snakes studied to date. Other features of chromatin condensation and morphology of the acrosome complex are similar to what has been observed in the Cottonmouth and Copperhead. Though the spermatids in P. platurus appear to be highly conserved, some differences in subcellular details are observed. These ultrastructural characteristics could be used to help determine the evolution of aquatic snakes from terrestrial snakes. Analysis of developing spermatids reveals morphologically conserved traits between different species along with subtle changes that could help elucidate phylogenetic relationships between snakes as more species are studied for spermatid characteristics.