The Strange Defense Mechanism of the Sea Cucumber

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The defense mechanisms animals use to evade or fight off predators can be both bizarre and fascinating. Some use camouflage or mimicry, while others have protective armor. Sea cucumbers, however, use one of the most unusual tactics we’ve seen. As you can see in the above video, they shoot their intestines out of their body when they feel threatened, a behavior called evisceration. Watch the video, and then let’s take a closer look at how and why they do it.

Sea Cucumbers Are Not for Salads

Despite their name, sea cucumbers have no connection to actual cucumbers. They are ancient marine invertebrates (echinoderms) and are related to starfish and sea urchins. There are thousands of different species, some of which have weird and whacky names like the sea pig (Scotoplanes globose), the headless chicken monster (Enypniastes eximia), and the gummy squirrel (Psychropotes longicauda). Sea cucumbers are found all over the world in both deep and shallow ocean waters and can be anything from less than an inch long to over six feet, and they have a huge variety of colors.

Vulnerable to Attack

Sea cucumbers are both slow and soft, which is just what a predator wants from its prey. They amble along ocean floors, feeding on nutrients hidden in the sediment in the same way that earthworms recycle nutrients in soil. However, they can also feed on plankton, algae, and some aquatic invertebrates.

Their bodies are soft and water-filled with very little in the way of a skeleton. Their skin is leathery and doesn’t have any protective spikes or spines that other ocean invertebrates have. All of this makes them very vulnerable and attractive to predators such as fish, crabs, turtles, and some sharks. They are also considered a delicacy in some Asian cultures.

Sea Cucumbers Fight Back

They may be slow and squishy, but sea cucumbers do not give up without a fight! Some of them have hooklike skeletal structures that they expose when they’re attacked, which makes them harder for predators to eat. But that is not the most impressive weapon in the sea cucumber’s armory.

As you can see in the above video, these amazing creatures can expel their intestines out through their mouth or anus (depending on the species), which is called a cloaca, by violently contracting the appropriate muscles. This may be a form of self-mutilation, but it is highly effective at startling predators and making them back off. In some species, the intestines are sticky, which makes them even more off-putting. More importantly, recent research has investigated the chemicals released by sea cucumbers during evisceration and found that they are highly toxic and are an effective repellent.

Recovering From the Attack

Believe it or not, sea cucumbers do not die when they have expelled their intestines. They are actually able to regenerate the missing and damaged body parts so that they can get back to their lives on the ocean floor. If we could discover how they do this, it could be invaluable for human medicine.