Chubby Little ‘Sea Pig’ Tastes More Like Poison Than Bacon

Regular pigs may roll around in mud, but sea pigs eat it. Om nom nom.

The life of the sea cucumber can be rather unfortunate, at least by human standards. Some shallow-water species have fish that swim up their bums and eat their gonads and sweet Moses I wish I were kidding about this. Really, sea cucumbers are mostly crawling segments of intestines, and they look delicious to a lot of creatures. Accordingly, a handful of sea cucumber species will defend themselves by firing their intestines and other organs out of their butts in the hopes of shocking their attackers. Again, not kidding about this.

Dive deeper, though, down past 3,000 feet, and you’ll find a variety of sea cucumber that’s living the good life—relatively speaking, that is. These are the little-studied sea pigs, half a dozen species in the genus Scotoplanes that do indeed look a bit like swine, if swine had way too many legs and ate mud instead of rolling around in it. Compared to their shallow-water cousins, sea pigs don’t have nearly as many predators, so they don’t have to bother dropping their guts out the back end. And good on ‘em for that, really.

Now, when you think sea cucumbers, you probably think of a tube of flesh, whereas the sea pig would appear to have limbs. In fact, these are known as tube feet, and while they’re super elongated in the sea pig, they’re found in other sea cucumbers too, plus their echinoderm compatriots, including starfish and sea urchins. These tube feet are connected to a “water vascular system”—that is, echinoderms have a ton of water coursing through them. That water helps give the sea pig its shape, while muscles in the legs allow it to wander around in search of food. Unfortunately, their body wall is also quite delicate: Catch one in a net and it’ll likely disintegrate, and it’s somewhat difficult to study a puddle of goo.

And those antenna-like things on top of the sea pig? Well, those are technically feet too, but they’re not there so the creature can keep walking if it flips over—though, let’s face it, that would be pretty sweet. No, these are thought to be specially adapted to help the sea pig find food in the pitch-blackness. “The animal can sort of smell areas of mud which have higher organic content,” says marine biologist David Pawson of the National Museum of Natural History. “And so you often find them in swarms, in great herds actually concentrated on areas of mud where there’s a high organic content.”

Unlike regular pigs, sea pigs are translucent. But I guess a pig ghost would be translucent. Doesn’t count though.

So, there’s this thing called marine snow. In the thousands of feet of water above the sea pigs, all manner of life is perishing and sinking to the bottom. And if you get yourself into a submersible and shine your light around, you can see it all snowing down, down, down, until it settles into the mud of the seafloor, which the sea pigs gobble up.

For this they’re equipped with around 10 tentacles—depending on the species—each with smaller structures that function like fingers. Planting these in the mud as they amble along, the sea pigs alternate moving the grub-filled tentacles to the mouth, all while facing against the current to get a whiff of any food “upstream.” The real bonanza, though, is when a whale carcass lands on the seafloor. As it rots into the sediment, hordes of sea pigs will scoot around it, gathering up the nutritious mud.

When they’re not gobbling marine snow or the occasional whale juice, sea pigs are going after all kinds of microbes on the seafloor. Which is just as well, because such microbes are consuming a whole lot of oxygen down there. When the sea pigs pass this microbial mud through their digestive system, they of course absorb all the good nutrients, but also themselves end up adding oxygen back into the muck and pooping it out on the seafloor. “They’re like earthworms,” says Pawson. “They sort of process the deep-sea mud and make it livable for other animals because they’ve increased the amount of available oxygen in it.”

Respiratory Trees, Self-Evisceration, and Other Things Sea Pigs Ain’t Got Time For
When it comes to breathing oxygen, sea pigs again betray their weirdness. Remember those shallow-water species of sea cucumber that have fish climb into their bums? Well, sea cucumbers also breathe through those bums, using a so-called respiratory tree. This is what those parasitic fish swim up, where they get a nice home and a constant supply of water to boot. But even if such fish lived in the depths, the sea pigs wouldn’t have to worry about them. They’re missing the respiratory tree. Instead, they breathe through their exceedingly thin skin, exchanging oxygen with the surrounding water right through their body wall.

Also setting sea pigs apart from other sea cucumbers: They don’t blow their guts out of their backsides when harassed. And that, according to Pawson, is probably because they don’t tend to get harassed that much. Compared to something like a reef, where all manner of predators can make life miserable for sea cucumbers, the deep is relatively safe. And think about just what a traumatic experience eviscerating yourself is (OK maybe don’t). Sure, the sea cucumber grows it all back eventually, but that takes a tremendous amount of energy. And in the deep, where food isn’t exactly plentiful, the sea pig probably wouldn’t have the resources to drive this regeneration.

Is a herd of sea pigs kinda cute, or is it just me? No? OK, I’ll sit down now.

Plus, they taste like death. “They have toxic chemicals in their skin, which makes them unpalatable to fishes and things like that,” says Pawson. Specifically, the nasty stuff is called holothurin, and is found in some other species of sea cucumbers (in fact, sea cucumbers in general are known as the holothuroidea). It’s so nasty, in fact, that peoples in the Indo-Pacific have been said to poison pools in coral reefs with the stuff to knock out fish for easy picking.

Still, for all science knows about the sea pigs (which, all things considered, is a good amount, given that it’s a deep-sea species), there’s much to be learned. How they mate is still a mystery, as is how long they live. “They might live for 10 years, or they might live for 100 years,” says Pawson. They leave tracks, which is a nice little clue, but “in some parts of the world’s oceans the rate of sedimentation, stuff falling from above down to the seafloor, is so slow that the tracks you’re looking at, even though they look fresh, they might be 100 years old.”

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