Some sea cucumbers empty almost their entire insides, through the mouth or the anus, then rebuild a new intestine within weeks. How can an animal lose its guts and grow them back from a simple fold of tissue left inside its body?
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In some groups of sea cucumbers, the animal ejects its digestive tract and other organs after cutting off one end of its body. Dendrochirotids usually do it from the front, while Aspidochirotids usually do it from the back.
The best-studied case is Holothuria glaberrima. After ejection, the torn edges of the mesentery, a membrane that holds the organs in place, form a rudimentary intestine stretching from the throat to the cloaca. A complete intestine rebuilds itself in a little over a month.
Another species, Holothuria forskali, instead expels small respiratory organs called Cuvierian tubules. These become sticky and can immobilise a predator. A lost tubule regenerates in about five weeks.
