A sea cucumber can eject much of its digestive system to evade attackers. This defensive behavior is called evisceration, a form of autotomy in which an animal deliberately sheds part of its body.
When threatened, a sea cucumber contracts its body-wall muscles and expels internal organs or tissues through the cloaca, an opening that also handles digestion and respiration. In some species, the ejected material can distract or entangle predators. Certain sea cucumbers also possess sticky or toxic structures called Cuvierian tubules, which may immobilize attackers and contain defensive chemicals.
The discarded organs are not permanently lost. Sea cucumbers can regenerate them over time, though the duration varies by species and organ. This behavior is not the same as a starfish everting its stomach to feed: sea cucumbers use evisceration primarily as an emergency defense. They are echinoderms, related to starfish and sea urchins.