Are Sea Cucumbers Poisonous? (Explained)

Sea cucumbers may seem defenseless, but they’re actually pretty tough animals. Since they’re relatively slow animals and can’t attack or escape their predators, they have developed other defense mechanisms that can efficiently scare off or even kill other animals. If you wonder if sea cucumbers can be poisonous or dangerous, I’ll talk all about that in this article. However, let’s begin with a quick answer:

Sea cucumbers, when threatened, can expel their organs with a highly potent poison called holothurin. In addition to that, the body wall of some species can be poisonous as well. The toxins in high amounts can be also dangerous to humans.

However, this certainly doesn’t tell the whole story. Below I’ll explain more about sea cucumbers’ toxins and how dangerous they are. Furthermore, I’ll explain what other defense mechanisms sea cucumbers have. Read on!

Are sea cucumbers poisonous to animals?

Even though sea cucumbers seem defenseless and harmless, they developed a unique defense mechanism. When the animal is disturbed, it ejects the sticky substance called Cuvieran tubules. It expels it through its anus or some through the mouth.

Cuvieran tubules are a highly potent poison known as holothurin. It can quickly weaken the enemy’s muscles, which usually scares them away efficiently. The experiment in California showed that the body wall of some sea cucumber species is toxic, but fish would still feed on them, avoiding poisonous parts.

Interestingly, the Cuvierian tubules aren’t only highly toxic but also very sticky and long. This may cause animals to get trapped, entangled, and efficiently repelled. It’s an efficient defense mechanism as sea cucumbers can’t really fight the predator.

Moreover, expelling tubules involves the loss of the gut, the water vascular system, and the haemal system. This sounds like a very problematic event for the lifespan of sea cucumbers, but this is where these animals become fascinating. They can grow their organs back within a few weeks!

Are sea cucumbers dangerous to humans?

Holothurin toxins aren’t only poisonous to animals but can be harmful to humans in high amounts. When with skin contact, sometimes it can lead to burning pain, itching, swelling of the area, and red-color skin. However, if they come into contact with the eyes, they may cause eye irritation or even permanent blindness.

If you happen to swallow holothurin, the result is muscle cramps, stomach pains, and in severe cases, death through respiratory paralysis. Remember that if you suspect that you got irritated by sea cucumbers’ toxins, it is always advised to contact a local emergency.

To decrease the pain, you can wash the injured skin with seawater that can dilute the toxin. Don’t use fresh water because it may increase the pain. If your eyes were affected, rinse them immediately and repeatedly with copious amounts of freshwater or saline solution.

Can sea cucumbers bite?

After we discussed sea cucumbers’ poison that makes them potentially dangerous to other animals, let’s discuss other potentially threatening behaviors such as biting.

Sea cucumbers don’t have teeth, so they can’t bite their predators. However, some species have developed “anal teeth”. Why, do you ask? Well, some fish, especially pearlfish, hide inside sea cucumber’s anus for protection. Some sea cucumbers don’t appreciate that their anus function as a shelter, and they have developed “anal teeth” to keep pearlfish out.

sea cucumber's teeth

What other defense mechanisms have sea cucumbers developed?

Sea cucumbers’ toxins are one of the most effective defense mechanisms they have developed. Sea cucumbers are very slow animals eating mostly waste particles and algae by picking them up with their feeding tentacles.

The animal can’t defend itself directly and fight predator, so it developed a defense strategy that prevent it from being eaten. Expelling Cuvierian tubules is one of the strategies, but sea cucumbers have a few more.

Another sea cucumbers’ extraordinary ability is that they can transform themselves into different states of matter. When these animals need to escape, they can pass through narrow spaces by liquefying their bodies and returning to a solid form again. It’s possible thanks to their unique collagen fibers in the tissues.

Another way to escape is to just simply swim away. Most of the time, sea cucumbers move by crawling around the seafloor. However, when threatened, some species can swim by lifting their bodies off the seafloor and rapidly flexing them. For instance, when touched by the arm of the predatory sea star.

Some sea cucumber species have the ability to clone themselves in response to the presence of predators. This process usually occurs in the larval stage when sea cucumbers haven’t developed other defense mechanisms. They divide their body into two or more parts and are a less obvious target as the copied larva is usually about half the size of the original one.

You can read more about sea cucumbers’ incredible defense mechanism in my other article: “Sea Cucumbers’ Incredible Defense Mechanisms”.


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