Wednesday, January 19, 2022

Like humans, female dolphins have a functional clitoris, study

The clitoris of dolphins is highly sensitive to tactile stimulation and is likely functional.

Dolphins are highly social. They have sex for social reasons as well as reproduction.

Scientists have known that dolphin vaginas contained inner flaps and folds for a long time. They also have a clitoris in the vagina in a spot that would make stimulation during copulation likely.

A new study reported that dolphin females- like humans- have a working clitoris. The findings are based on the discovery that the clitoris-like structure positioned in the vaginal entrance of bottlenose dolphins has lots of sensory nerves and erectile bodies.

In this study, scientists closely observed the dolphin clitoris from 11 females who died naturally. They studied them for the presence, shape, and configuration of erectile bodies. Later, they examined how nerve fibers ran through the tissues.

Patricia Brennan, an assistant professor of biological sciences at Mount Holyoke College in Massachusetts, said, “Just like the human clitoris, the dolphin clitoris has large areas of erectile tissue that fill up with blood.”

“The erectile tissue shape changes as animals become adults, suggesting that it acquires a functional role.”

The clitoris body was found to have large nerves. Plus, it has many free nerve endings right underneath the skin, which is much thinner than in the adjacent skin.

Macro and microanatomy of the dolphin clitoris
(A) Clitoris location in situ, with the urethral canal filled with silicone and cut open. UC, urethral canal; CB, clitoris body; CH, clitoris hood; V, vestibule. Scale = 1 cm. (B) 3D reconstruction from DiceCT scan of the erectile bodies of the clitoris of an adult female. Elongated crurae clitoridis (CrCl) meet in the erectile tissue of the clitoral body (ErCB). Anterior view. Scale = 1 cm. (C) Midsagittal aspect of the clitoris in an adult female. Two types of erectile tissue can be distinguished: CC, corpus cavernosum, and ST, spongy tissue. (D) Dermal papillae (DP) of the clitoral skin showing large and abundant axons in the papillae (arrowhead) (Bielschowsky silver stain, axons: black/brown) 100X. (E) Coronal section of the clitoris (plane shown in C, dotted line), Gomori’s one-step trichrome stain (collagen: green; nuclei: black; cytoplasm, muscle fibers, and keratin: red). Abundant nerves (N) below the dermis are followed by spongy tissue that is surrounded by tunica albuginea (TA). 1.25X. (F) Genital corpuscles (GC) of different sizes are abundant close to the epidermis (positive staining with PGP9.5) 50X. (G). Coronal section of nerves in the clitoral body (positive staining with PGP9.5), next to an artery (A). 20X. Credit: Cell Press

Scientists also found genital corpuscles much like those previously described in the human clitoris and penis tip. The genital corpuscles are involved in the pleasure response.

Brennan says, “Overall, the erectile bodies in dolphins are “surprisingly similar” to the shape of the erectile bodies in humans.”

“Since the entire pelvis of dolphins is so different to humans, it was surprising to see how similar the shapes were. Also, the size of the nerves in the clitoris body was very surprising. Some were larger than half a millimeter in diameter.”

“They got curious about the dolphin clitoris while studying the evolution of vaginas in dolphins.”

“Every time we dissected a vagina, we would see this very large clitoris, and we were curious whether anyone had examined it in detail to see if it worked like a human clitoris. We knew that dolphins have sex not just to reproduce but also to solidify social bonds, so it seemed likely that the clitoris could be functional.”

“Studying and understanding sexual behaviors in nature is a fundamental part of understanding the animal experience and may even have important medical applications in the future.”

Scientists will continue to examine the clitoris and genitalia of dolphins and many other vertebrates to help fill in these gaps.

Journal Reference:

  1. Patrica L. R. Brennan et al. Evidence of a functional clitoris in dolphins. DOI: 10.1016/j.cub.2021.11.020

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