Abstract:Genitalia are morphologically variable across many taxa and in physical
contact during intromission, but little is known about how variation in form
correlates with function during copulation. Marine mammals offer important
insights into the evolutionary forces that act on genital morphology because
they have diverse genitalia and are adapted to aquatic living and mating.
Cetaceans have a fibroelastic penis and muscular vaginal folds, while pinnipeds have a baculum and lack vaginal folds. We examined copulatory fit
in naturally deceased marine mammals to identify anatomical landmarks
in contact during copulation and the potential depth of penile penetration
into the vagina. Excised penises were artificially inflated to erection with
pressurized saline and compared with silicone vaginal endocasts and within
excised vaginas in simulated copulation using high-resolution, diffusible
iodine-based, contrast-enhanced computed tomography. We found evidence
suggestive of both congruent and antagonistic genital coevolution, depending
on the species. We suggest that sexual selection influences morphological
shape. This study improves our understanding of howmechanical interactions
during copulation influence the shape of genitalia and affect fertility, and has
broad applications to other taxa and species conservation.
Citation:Orbach DN, Kelly DA, Solano M, Brennan PLR. 2017 Genital interactions
Cheers,
Dara Orbach, PhD
Izaak Walton Killam Postdoctoral Fellow
Whitehead Lab
Department of Biology
Dalhousie University
Research Associate
Brennan Lab
Department of Biological Sciences
Mount Holyoke College