Sea Cucumbers Can Expel Their Internal Organs as a Defense Mechanism

This startling act of self-defense, known scientifically as evisceration, is a complex biological process. When a sea cucumber feels threatened, it violently contracts its body wall muscles, causing a tear in its cloaca. A specialized type of connective tissue, which the animal can soften at will, liquefies around the organs designated for expulsion. This allows it to forcibly eject a sticky, toxic mess of internal organs, such as parts of the gut and respiratory trees, at the would-be predator. Some species also unleash hundreds of stringy, adhesive strands called Cuvierian tubules, which expand up to 20 times their original length upon contact with water, effectively entangling and immobilizing attackers.

The ejected organs serve as both a physical net and a chemical weapon. They contain potent toxins called holothurins, which can deter or harm predators. This dramatic event is not fatal but rather a temporary inconvenience for the sea cucumber. Having successfully distracted its enemy, the creature crawls away and begins one of nature's most incredible feats of regeneration. It can survive for several weeks without its key internal systems, sometimes absorbing nutrients through its skin, while it regrows all the lost organs. This entire regenerative process, which scientists are studying for its potential applications in human medicine, can be completed within a few weeks.