Mnemiopsis leidyi is a small marine animal that never ceases to amaze... Phylogenetically close to jellyfish, this small, 5 cm long creature has long interest marine biologists. In 2016, they discovered that it does have a digestive system. But despite their observations, they never saw the animal defecating. And for good reason: its anus only appears when it wants to do its business, and then disappears!
While some species of jellyfish have a single opening to ingest food and also to expel waste, others, called ctenophores, have an anal opening closed by a sphincter. They therefore have two distinct openings for ingesting and eliminating.
What amazed scientists is that Mnemiopsis leidyi has none of these characteristics. Once its bowel is full, this unique animal fuses its skin with the intestinal wall, and creates an opening that then disappears once its needs are met. This amazing process is very fast because there is only one layer of cells between the skin and the intestine.
A unique fact in the animal kingdom
This case of 'transient anus' is unique. This is the first time that such a phenomenon was observed on an animal. Sidney Tamm, a researcher with the Marine Biology Laboratory at the University of Chicago, participated in the study of this very particular invertebrate. He watched images taken over several days of the animal. Its anus appears and disappears on its skin at regular intervals: between 10 minutes in the larva and approximately every hour in the adult.
The results of this research were published in the journal Invertebrate Biology. A researcher commented in an interview for New Scientist.
This is a truly spectacular sighting. To my knowledge, there is no other documented case of transient anus in the animal kingdom.
Mnemiopsis leidyi most often lives near the shores of the American continent, but can also be found in the Black Sea and the Caspian Sea. It enjoys shallow water and feeds mainly on plankton.
Take a look at the video above to see more of this bizarre creature for yourself...