This Jellyfish Has a Butthole That Only Appears When It Poops

In a newly published paper in the Invertebrate Biology journal, a biologist made a discovery believed to be unique in the world of animal life.

The species of jellyfish Mnemiopsis leidyi, commonly referred to as a warty comb jelly or sea walnut, was found to have no anus until it needs to defecate.

The abstract of the paper states, "Contrary to the scientific literature, individuals defecated through only one of the two anal canals which possesses the only anal pore. The anal pore was not visible as a permanent structure as depicted in textbooks, but appeared at defecation and disappeared afterward."

The species of jellyfish is unique in and of itself because most jellyfish eat and defecate with the same orifice, but the Mnemiopsis has at least one anus separate from its mouth.

The researcher learned that the jellyfish has no permanent anus which connects to the gut. Instead, when the jellyfish has enough accumulation of food waste in its gut, the gut expands far enough outward that it eventually reaches the epidermal layer and forms an anal opening. After defecation, the opening seals itself and is not detectable as a feature on the jellyfish.

Sidney Tamm of the Marine Biological Laboratory in Woods Hole, Massachusetts, made the discovery. “There is no documentation of a transient anus in any other animals that I know of,” he says. Tamm wants to use a powerful electron microscope to study the anus further and is looking for the feature in other species of comb jellyfish to find some connection for evolutionary purposes.

Photo Credit: Getty Images

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