snakes have a “double” clitoris

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Researchers from La Trobe University and the University of Adelaide in Australia, as well as the University of Michigan Museum of Zoology, have made the first ever anatomical description of the clitoris of female snakes. Their study raises questions about the dynamics of snake mating and suggests that these animals could also feel pleasure during sex.

Female genitalia are strikingly neglected compared to males, limiting our understanding of sexual reproduction in vertebrates “, emphasize the authors of the study. Previous research had mistaken these genitalia for scent glands or underdeveloped versions of penises. However, it turns out that, like male snakes, which have hemipenis – a pair of genitals covered by keratinized spines – female snakes have not one, but two individual clitoris, the hemiclitoris, separated by tissue and hidden under the animal’s tail.

Megan Folwell, a PhD student at the University of Adelaide and first author of the study, believes there is some sort of taboo surrounding female genitalia, which explains why these hemiclitoris were not identified earlier. ” I think it’s a combination of not knowing what to look for and not wanting to… “, she told Guardian. Remember that it was only very recently that a team of American researchers established the number of nerve endings in the human clitoris (which had been underestimated for years).


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Very variable morphologies depending on the species

This study thus constitutes the very first complete description of the clitoris of female snakes. However, it was not easy to observe this organ because some are extremely small, says the scientist. Examination of a dead worm (Acanthophis antarcticus), a common species in Australia, however, has allowed in-depth morphological descriptions to be made: this species has a relatively prominent, heart-shaped clitoris.

Image of a female Acanthophis antarcticus specimen. (b) Ventral view of a three-dimensional DiceCT model of the specimen and dissection (CL = cloaca; HC = hemiclitoris; SG = scent glands). © Luke Allen (photo of the viper)/MJ Folwell et al.

Histology revealed the presence of erectile tissue, which can swell with the influx of blood, and bundles of nerves—features similar to those in the mammalian clitoris. ” The innervation and erectile tissue of the hemiclitoris, as well as their position near the posterior lip of the cloaca, where the skin is thinner, could allow stimulation during mating “, add the researchers.

The team also used bioimaging and dissection techniques to study a dozen other snakes from nine different species. The shape and size of the clitoris varied greatly between species, ranging from less than one millimeter to seven millimeters. ” Some clitoris are quite muscular and large – in vipers for example – but they are very thin, elongated and small in other snakes says Dr. Jenna Crowe-Riddell, postdoctoral researcher in neuroecology at La Trobe University and co-author of the study. The researchers note that courtship and mating differences between species may have influenced the evolution of hemiclitoris morphology.

Histology of the hemiclitoris and scent glands of a dead worm. (a) Red blood cells in the right hemiclitoris and muscle layer between the hemiclitoris and cloaca; (b) right hemiclitorial nerves; (c) red blood cells and collagen in the right hemiclitoris. C = collagen; CL = drainage well; HC = hemiclitoris; M = muscle cells; N = nerve fibers; NB = nucleated red blood cells; SG = scent glands. © MJ Folwell et al.

This finding confirms that the hemiclitoris has been preserved in squamates – the scaly reptiles that regularly shed their skin, such as snakes and lizards – and provides preliminary evidence for differences in this structure between snake species. which can be used to better understand the systematics, reproductive evolution and ecology of these reptiles.

A functional role that remains to be clarified

Histological characteristics of the clitoris suggest that they have “functional importance in mating,” the researchers point out. They speculate that these hemiclitoris could provide a stimulatory signal that drives vaginal lubrication—a mechanism that would help protect the female from damage that can be caused by the keratinized spines that cover the male organ; these thorns serve in the form of small hooks to hold the male genitalia in the female’s body during mating.

They can also be used to trigger ovulation and signal the fallopian tube – which carries eggs to the uterus – to prepare for sperm storage. This study may help understand female mate choice, but raises many questions about snake mating dynamics.

It is possible, according to the study authors, that the hemiclitoris transmits sensation to female snakes during courtship and mating, which may promote longer and more frequent matings, leading to increased fertilization success.

According to Dr. Crowe-Riddell’s next thing to do is to look at other species of snakes and how they mate, to determine whether they do so under duress or rather out of attraction and pleasure. ” Now that we know this anatomy, we can reverse the coercion hypothesis and say it could be seduction, which hasn’t really been considered for snakes. […] I think the snakes were left out because they are scaly and kind of weird said Dr. Crowe-Riddell.

Source: MJ Folwell et al., Proceedings of the Royal Society B

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