Research in Dr. Iske Larkin’s Laboratory

Reproductive anatomy and histology of male manatee (Trichechus manatus latirostris)

This work is being conducted by Jonathan Cowart for his PhD Dissertation work with Dr Larkin to be presented in 2019

Current research focuses on studying multiple reproductive parameters in male Florida manatees including assessing normal gonadal function through immunohistochemical analysis, defining baseline information for semen parameters through objective computer-aided sperm analysis, and investigating phylogenetic relationships for these reproductive parameters between manatees, elephants, and hyraxes, which are closely evolutionarily related to each other. This research will help establish reference points for future research and will shed light on individual, developmental, and seasonal changes in reproduction.

Figure to the left: Imaged is a single seminiferous tubule within the testis showing all stages of spermatogenesis (spermatogonia, primary spermatocyte, secondary spermatocyte, and early and late spermatids). The brown coloration indicates a cell that is currently going through a mitotic division (i.e. cell proliferation) and shows that many cells within this tubule are either actively going through a division or are coming to the end of a division (that’s why some primary spermatocytes are staining brown because they are just at the end of the spermatogonia dividing and becoming a primary spermatocyte but before the primary spermatocyte undergoes a meiotic division).

This work was conducted by Hilda Chavez for her MS-Thesis 2015 with Dr Larkin

In order to improve the assessment and population maintenance of the Florida manatee (Trichechus manatus latirostris), the study of the reproductive physiology and anatomy can be an important role. The study of male reproduction in this species is low, with some publications related on the general description of the reproductive tract and sperm competition. It is known that mating behavior for manatees is described as “promiscuous”, where several males pursue an estrous female for up to 6 weeks. However, only a single male will be the one to fertilize the female with a single calf born (twins are rare). The goals of this research are to characterize, at the gross and histological level, the male reproductive tract, including accessory sex glands, using a variety of different tissue stains including trichrome, PAS and immunohistochemistry. We hope to address hypotheses related to the male manatee role as a sperm competitor.

Manatee Sensory Sytems Research in Dr. Roger Reep’s Laboratory is located under Comparative Neurological and Sensory Physiology.