Functional Morphology of the Dolphin Clitoris

Abstract

Dolphins copulate year‐round despite short estrus periods. Copulation may be pleasurable for female dolphins through clitoral stimulation, as they have large and well‐developed clitorises. Although female mammals possess a clitoris homologous to the penis, the general structure and functional morphology has only been described in a few species. We explore the gross morphology and microanatomy of the common bottlenose dolphin (Tursiops truncatus) clitoris at different developmental stages to assess the potential for erectile tissue to expand during copulation. Excised clitorises were collected opportunistically from eleven post‐mortem dolphins including adults, subadults, and calves. Specimens were subdivided for use in: 1) gross morphology dissections, 2) micro‐computed tomography scans, or 3) paraffin histology and staining (modified Mason's trichrome and hematoxylin and eosin). Erectile tissue was present consistently along the clitoral body that extended from the hood tip to the base. The erectile tissue had a forked shape and similar relative volumes in both the calf and subadult specimens. The erectile tissue was surrounded by a thick layer of smooth muscle along the lateral sides of the crurae, clitoral body, and hood, but not cranially or caudally. Muscle tissue was surrounded by connective tissue. There was a hard bulb with a capsule around it at the root of the clitoris proper that was comprised of dense connective tissue. It appeared to be structural rather than erectile or secretory in nature. Our data provide a baseline for comparisons with other species known to have sex for pleasure (e.g., humans). The consistent shape and relative volumes of erectile tissues between calves and subadults suggest there are few developmental changes except for allometric size increases. Future research that compares the density of connective tissue in cetaceans and other marine and terrestrial mammals may be able to yield insights if the unexpectedly dense tissue of the dolphin clitoris is an adaptation driven by natural selection or sexual selection.Support or Funding InformationThis research was funded by the American Association of Anatomist Short‐term Visiting Scholarship to D.N.O. and a faculty grant from Mount Holyoke College to P.L.R.B.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.