Welcome to brain Stuff from How Stuff Works. Hey, brain Stuff, Lauren vocal bamb Here. You probably have a favorite sea cucumber and don't even know it. There are over one thousand, two hundred species in the world's oceans, so many that scientists are even confused about exactly how many there are, So there's probably one you'd like a lot. Some of them are decked out with the colors of your favorite sports team. Others look like somebody crocheted and oversized zucchini
out of brown aquylic yarn. Even if you weren't particularly interested in a living sea cucumber, you might want to eat a dead one, or even tape one is medicine. But if you don't know already and had to guess, would you bet a sea cucumber is an animal or a vegetable. They tend to come in tube form, like a sweet potato of the sea. They look vegetable ish, but they are in fact animals. The thing where we
refer to them as cucumbers doesn't help. But they're a chinoderms, a phylum of marine animals that also includes starfish sea urchins. Everybody in this spylum has what's called pentameral symmetry. They have five arms arranged around a center point. Of course, the kindest thing you can say about a sea cucumber's physique is that it looks like a large hogi bun
that you wouldn't want to eat. But though it more closely resembles a slug than a star, the five rows of tube feet that extend from its mouth to its anus give it the same basic layout as say, a very elongated sea urchin that fell over on its side. Sea cucumbers have a different approach to reproduction than we do. They are usually born either male or female, but can change from one to the other during their lives. They communicate with each other by releasing hormones into the water,
which is very similar to their style of reproduction. They expel their gam meets those are the egg and sperm cells out into the water column and just assume that they'll find each other, just as they assume that their friend got the hormone message that they left. Sea cucumbers eat tiny animals, particles of algae, and general sea junk out of the water using frilly tentacles that between meals,
they keep hidden in their mouths. What they have in the way of a brain is a ring of nerve cells around their mouth that tells them when it's time to eat, burrow into the sand, walk somewhere, or attack. And even though they look like tube socks filled with modeling clay, a sea cucumbers defense mechanism is pretty terrifying. Imagine you're rough housing with a friend or sibling, or
maybe taking a martial arts class. I'm willing to bet that your opponent's defense mechanism would not be to shoot out some of his respiratory organs at you out of his rear. But that's what ce cucumber combat looks like. They have the amazing ability to regenerate the organs that they lose this way. Some species but out sticky string like spiderwebs to trip up, or and snare their enemies, while others have a special toxin that kills or stun Small animals don't mess with sea cucumbers, but we do
mess with c cucumbers all the time. Some species are at risk of extinction because in some Asian countries, sea cucumbers are the ultimate luxury snack. Some tropical species can go for between ten dollars and six hundred dollars per kilogram dried in mainland China, and one type retails for three thousand dollars per kilo. Sea cucumbers are also used in Chinese medicine to treat a variety of ailments like muscle aging, compromised immune system, fatigue, and arthritis. Some even
suggest they could be used in cancer treatments. The varieties that are used in food or medicine are becoming increasingly rare due to over fishing are over cucumbering. As a result. There are around three hundred and seventy seven species of sea cucumbers on the Red List of Threatened Species put out by the International Union for Conservation of Nature. Seven of these are classified as endangered and nine as vulnerable.
But we need sea cucumbers. Not only are they economically important as a seafood, they are essential to ocean ecosystems. They're important filtration systems for watery habitats all over the world. In some places in the deep ocean, vast herds of sea cucumbers roam the ocean floor, gobbling up to tritus that drifted down from above. Plus some species provide vital
services for other marine life. The pearl fish, for instance, takes refuge in a c cucumber's anus, and sometimes entire schools of pearl fish can find shelter in the rear end of a single ce cucumber. They usually don't mind much unless they're trying to use their anus to breathe at the moment. Oh yeah, c cucumbers breathe through their anuses. I forgot to mention that part. Today's episode was written
by Jesselyn Shields and produced by Tyler Clay. For more on this and lots of other bizarre topics, visit our home planet, how Stuff Works dot com.