SNAKE REPRODUCTIVE ANATOMY
- kradiganscience24
- Mar 19
- 3 min read
Tavishi
Yesterday I was feeding my friend Samyak's Mexican black king snake when I realized I don't really know much about snake reproduction. I assumed from what I know about birds and other reptiles that it was kinda just a cloaca situation, but I quickly realized there's so much more to the process of making more snakes than meets the eye.
I was in fact correct about the cloacas, though.
Both male and female snakes have cloacas. A cloaca is just one urogenital opening serving as an exit for the digestive, reproductive, and urinary systems of the body. Cloacas are the rear orifice for pretty much all animals except mammals (with, of course, a few key exceptions.)
Internally, male snakes have two testes, with each testis associated with one hemipenis. The testes are the site of sperm production, and are tucked inside the snake close to the kidneys. The right testicle lies above the left testicle, and is very close to the vena cava. The left testicle, however, is closer to the kidney and the adrenal gland. It is less close to the vena cava, and thus, has its own testicular blood vessels.
On the other hand, mammalian testicles descend, and often have comparatively longer epididymises and other structures of the testicle. For the most part, other than minor testicular architectural differences (see arrangement of Sertoli and Leydig cells), reptile testicles remain very similar to mammalian testicles.
Each testes connects to a hemipenis by a vas deferens, a duct which pretty much just shuttles sperm out of the body. However, whereas in humans, the vas deferens is found within the penis, in snakes, the vas deferens instead deposits sperm into the sulcus spermaticus, which develops from ectoderm tissue that is originally part of the germ layer that gives rise to the hemipenis.
The hemipenis itself is also able to be tucked inside the snake body, despite being part of the cloaca itself. Male snakes have something called a sulcus, which is different from the sulcus spermaticus (if you haven't caught on, the sulcus is an anatomical term for a storage unit), which is where the hemipenises are stored when not being used for copulatory activities. For better grip, the hemipenis is hooked and textured.
Female snakes, as humans do, have two paired ovaries. Each ovary contains a bunch of oocytes (later giving rise to eggs!) Surrounding the oocytes is a mesovarium, which is a thin tissue layer also present in humans that is from the peritoneum of the uterus (outer layer). A major difference between a human and snake ovary is that humans have an ovarian medulla, whereas snakes lack such. Rather than using the space for tissue and blood vessels, snakes, rather, just have a hollow space.
Just as the left testicle in males is caudal to the right testicle, the ovaries follow the same structure, with the left ovary having its own ovarian blood vessels, but the right ovary connecting to the vena cava. Additionally, the left ovary is often less developed than the right ovary.
Other than that, snake internal anatomy remains similar to a mammal. However, snakes do lay eggs... and we don't.
After ovulation (ovum leaves ovary), the ovum goes through the oviduct, consisting of three regions: the infundibulum, magnum, and uterus. The magnum is the site of albumin deposition into the future egg, and the uterus is where the actual membrane and shell is formed. Within the oviduct is the receptaculum seminis, a site of sperm storage. This can store sperm for months, even years, allowing for fertilization even following a long period of abstinence.
Finally, once the egg is finished being made, it is deposited into the urodeum, a part of the cloaca, where it is later laid and matures.
Note: this was my first time illustrating a Kradigan post. I've generally used most online images, but I couldn't quite find any good references. Thus, I decided to illustrate pretty much all of it. I will leave y'all with silly snak.
Credits to Apophis, Samyak's snake!
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