Sanibel Sea School Blog

Cucumbers of the Sea

April 12, 2021

By Emily White

If you know where to look, it’s relatively easy to find sea cucumbers lazing on the ocean floor, slightly buried in the sand- but make no mistake, these critters aren’t anything like the crunchy vegetable that you might be used to eating with your salad. Sea cucumbers are pretty important to the balance of the ocean- they’re filter feeders, and they spend most of their days slowly crawling along the ocean floor, filtering sand through their tentacles to find nutrients and clean up along the way.

There are over a thousand species of sea cucumbers that vary in shape, size, and color, but the variety that you’re likely to spot on Sanibel Island is Holothuria floridana, also known as the Florida Sea Cucumber. As the largest American species of sea cucumbers, H. floridana can grow to be up to 8 inches long, with tough, leathery skin and conical projections that look like tiny, dull spikes.

Sea cucumbers have a couple of really interesting defense mechanism against predators. The first is by expelling their Cuvierian tubules, which are sticky, toxic white threads that can entangle anything that comes too close. This is especially useful for slow predators like sea stars, who won’t be able to quickly evade the threads, but faster animals can also get stuck if they aren’t careful.

Sea cucumbers can scare off predators by expelling the rest of their organs as well. It might sound a little wacky, but if a sea cucumber has to resort to this in order to stay safe, it can grow its organs back afterwards! Because of this cool skill, scientists are trying to learn about sea cucumbers so that someday, we might be able to able that knowledge to healing human injuries.

Check out this video from National Geographic to learn more about sea cucumbers, and to watch those Cuvierian tubules in action!

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