Comparison of Vagina Morphologies between Little skates (Leucoraja ocellata) and Winter Skates (Leucoraja erinacea)

Abstract

The reproductive tract of skates has been studied for several decades, but despite the fact that skates have internal fertilization, there has not been any mention of a vaginal structure in this group that could be involved in copulation. For my thesis study, I examined two sister species of skates, Little and Winter skates, to answer several questions: 1): Is there a distinct contrasting structure in the cloaca of the female vs. the male skates to determine that they have a vagina? 2): If so, is there a significant difference in the shape and size of Winter and Little skate vaginas? 3): How does vaginal shape vary according to body size within each species, and Finally, because male skates have intromittent reproductive organs called claspers, we wanted to determine if female Little skates had adapted their vaginal tissue for copulation with the hooked claspers of the male Little skate, and compare these to the Winter skates, where the males have claspers that lack a hook. In order to do this, we examined the vaginal tissue using histology (stains: Masson’s Trichrome and H & E). This work highlights the importance of examining female morphology in detail to understand the evolution of genitalia.