Ultrastructure of the Spermatozoa from a Florida Manatee (Trichechus manatus latirostris)

Semen was opportunistically collected from a free-ranging, 10-year-old, 275 cm (total length) Florida manatee (Trichechus manatus latirostris) during rehabilitation treatments. Ultrastructure of the spermatozoa was examined b y scanning and transmission electron microscopy and differed slightly from that described for other mammals. Comparisons to the manatee's closest phyl ogenetic relatives, the elephant and hyrax, were made. The manatee spermato zoa had a similar acrosome but a distinct annulus and lacked the dense bodi es observed in the neck of the elephant spermatozoa. Additionally, manatee spermatozoa lacked the lateral vacuoles observed in the nuclear chromatin f rom of the hyrax spermatozoa. These data add to our understanding of manate es and allow for comparative studies with other species that may be useful in phylogenetic and reproductive studies.