Meeting Abstract
Sperm characteristics, such as morphology and ultrastructure, constitute distinctive, evolutionary features of each individual species. Therefore, the spermatozoon is a useful element for studying the evolution of a particular species as well as the phylogenetic relationships between species. This study compared spermatozoal characteristics from three related species, the manatee, elephant, and hyrax, to further explore evolutionary and phylogenetic relationships. Morphology and morphometry were analyzed using a Sperm Class Analyzer computer-aided sperm analysis system (CASA) and ultrastructure was analyzed using scanning and transmission electron microscopy. Many ultrastructural similarities were found to exist between all three species. Each of the three species exhibited similar mitochondrial numbers, acrosomal coverage, and a unique similarity in the size of the outer dense fibers with an enlargement of 1, 2, 5 and 6. However, marked differences were apparent in the hyrax spermatozoon. The hyrax spermatozoon was notably different in both morphometry and overall shape and lacked a distinct diminishment along the equatorial acrosomal region, which was apparent in both the manatee and elephant. While many similarities exist, which highlights the unique phylogenetic relationship between these three species, the spermatozoon characteristics appear to be most similar amongst elephants and manatees suggesting a possible coevolution throughout time.
