Probably More Than You Want to Know About Sea Cucumbers

Probably more than you want to know about sea cucumbers

What’s lumpy, squishy, and breathes through its butt? This guy. Meet the Sea Cucumber, one of many ocean-dwelling animals that are likely to make people say “ew.” But let’s not judge on first appearances – these tubular creatures are pretty neat.

There are over 25 species of sea cucumber in BC alone so, for the sake of the article, I’ll be thenceforth referring to the charismatic and spectacular California Sea Cucumber (Parastichopus californicus). Despite California’s claim on the name, these magnificent lumps can be found from Northern Mexico all the way to Alaska. If you’ve ever gone exploring at an exceptionally low tide and seen a purple/red blob that looks like it couldn’t possibly be a living creature, then you’ve probably seen our cucumber friend.

So what are sea cucumbers anyway? First and foremost, sea cucumbers are animals. They eat, they poop, they breathe, and they reproduce. More specifically, they are invertebrates of the Echinoderm phylum (a group of animals that also includes urchins, sand dollars, and the oh-so-loved sea star). What’s so special about cucumbers? Everything.

Upon first glance, California Sea Cucumbers are fairly alarming. These magnificently tubular beasts can reach lengths of 50 cm and are covered in aggressive-looking spikes. They look less like cucumbers, and more like something out of Monsters Inc. – like a giant, raw sausage that grew thorns and came to life. They have no eyes, but they do have “front end” designated by a large mouth full of “feeding tentacles.” These plumes of branching tentacles are covered in thick, sticky mucus that allows the cucumbers to eat sediment and decomposing organic material (yum).

Despite an aggressive first impression, sea cucumbers are actually big softies, and I mean that literally – they have no bones. Even their threatening spikes are quite soft to the touch. The vast majority of their bodies are composed of sea water. In fact, like other echinoderms, sea cucumbers don’t even have blood – instead they make use of something called a “water vascular system.” The flow of sea water through their body cavity serves to transport nutrients, oxygen, and even creates a hydraulic system that powers their movement.

Have you ever turned over a sea star and seen thousands of tiny tubes on the underside of their arms (if not, use your imagination… or Google)? Those are called “tube feet” and they are how most echinoderms move around. Each tube foot is a wee, hydraulic-powered suction cup. When the thousands of tube feet work in concert, they can move the rest of the body along the ocean floor, up rocks, even along the underside of an overhanging rock (albeit, very slowly).

Here’s where things get interesting (and where children should probably cover their eyes).  

It is time to talk of the anus. The back-end of a sea cucumber is a fascinating place. Not only is it used for the conventional purpose; it is also from whence a sea cucumber draws breath. The respiratory tree, a cucumber version of lungs, is located in the posterior and is responsible for drawing oxygen from sea water that is breathed in and out through the derrier. Fun, eh?

The bum of a sea cucumber is also a much sought-after location for an utterly strange parasitic organism called a pearl fish. This narrow little punk of a fish will swim into the back door and sit comfortably inside, enjoying the protection, ‘fresh’ water, and an occasional snack of sea cucumber gonads. A truly unfortunate sea cucumber can be a host to upwards of ten pearl fish at a time. Luckily, sea cucumbers have a trick up their sleeves (or rather, up their butts).

“Evisceration” is the remarkable ability to expel one’s innards. There are a number of things that might cause a sea cucumber to eviscerate – a pearl fish infestation certainly is a good reason, as is an ill-placed foot of a tide pool explorer, or an aggressive encounter with a predator. Sea cucumbers can push their guts out through their mouth or through their tush. Even more remarkable is their ability to regrow these lost organs in a matter of weeks.

So there you have it, all you could ever want to know about sea cucumbers (and probably more).

Written by Emily Beeson