When it comes to crazy party tricks, the warty comb jelly has everyone beat. New research shows that these transparent sea creatures are able to sprout a fresh anus every time they poop. When they are done with their bathroom break, the newly formed butthole vanishes without a trace.

A video of the warty comb jelly expelling waste (shot in 2016 prior to the discovery of its 'transient' anus).

“There is no documentation of a transient anus in any other animals that I know of,” Sidney Tamm, author of the new study and biologist at the Marine Biological Laboratory in Woods Hole, Massachusetts explained to New Scientist.

The warty comb jelly (Mnemiopsis leidyi) or sea walnut belongs to a group of jellyfish-like creatures called ctenophores. The see-though ocean dwellers are descended from one of the oldest animal lineages and have ancestors that lived in the Cambrian period some 525 million years ago. Unlike true jellyfish which have a single gut opening that functions as mouth and anus simultaneously, ctenophores have a through-gut with some species even lucky enough to sport multiple poop-chutes.

In the case of the sea walnut though, Tamm struggled to track down even a single anus. “It is not visible when the animal is not pooping,” Tamm told New Scientist. “There’s no trace under the microscope. It’s invisible to me.”

Using video microscopy, Tamm was able to observe the comb jelly’s unique defecation routine. As waste builds up in the animal’s gut (or gastrodermis), it balloons out until it touches the outer layer called the epidermis. Once there, gastrodermis and epidermis fuse to form an anal opening which closes up after excretion.

Warty comb jelly anus in action. (Tamm, Invertebrate Biology, 2019)

Because the gut and epidermis are only a single cell layer thick the process is pretty speedy. Warty comb jelly larvae grow an anus every ten minutes, while the five-centimetre long adults stick to an hourly routine.

Tamm believes that the new discovery could help us better understand how single-orifice organisms made the transition to a through-gut. The comb jelly’s intermittent anus could represent the evolutionary groundwork that gave rise to modern digestive tracts and nervous systems.

So next time you’re on the loo, spare a thought for the sea walnut and gives thanks that your butthole is easily locatable.


Header image: mark6mauno