Sea Pigs Like Mud Too
Sea Pigs are a group of sea cucumbers that live at great depths and pressures. They are some of the most commonly seen creatures on the sea floor, sometimes aggregating in the hundreds.
Sea Pigs are detritivores meaning they eat fallen waste and organic matter. They have oral tentacles they can use for filter feeding or shoving sand in their mouths. They like to hang around whalefalls eating scraps and waste-heavy soil made by other creatures as they eat the whale.
Like us, their bodies are held together by a protein called collagen. Sea pigs are able to change the stiffness of their collagen. Whenever they want to bend, they release softenin, a protein that makes their skin less stiff. And whenever they stop, they release tensilin, which makes it more stiff. These proteins can actually be found in most echinoderms like starfish, sea urchins, and sand dollars. They use this ability to stand upright above the sea floor without using expensive muscles. This increases their surface area so they can take in more oxygen through their skin.
When stressed, they're able to evicerate themselves! That sounds very dramatic, and it is! They'll shoot out their internal organs, potentially laced with a potent toxin. Sea cucumbers in general have a poison called holothurin, a powerful soap that ruptures cell walls, but I couldn't find a paper saying sea pigs have it specifically. After expelling their organs at you, they can slowly regenerate them.
They do have muscles, but they don't use them as directly as we do. They have a water vascular system, which means to move they use their muscles to pump water into tiny chambers all throughout their limbs. Here's a starfish water vascular system for example, starfish use external sea water so it's a little different.
They have anntennae on their back which are structurally the same as their feet. They may use these to feel out predators, or to help them swim. Yes, they swim! The species in this video below clearly spends more time swimming than others. It has webbing between its antennae and backmost legs.
A lot of sea pigs are found with parasites or infectious tumors embeded in them, but one relationship stands out. 96% of juvenille king crabs were found riding sea pigs! Your pet sea pig even has a crab riding it! Most things know not to eat sea pigs because they're gross, (and maybe poisonous), so the crabs will hide underneath them.
(They're Friends!)
They are very likely the cutest echinoderms and it's really enchanting to watch them eat sped up. However, it's very likely they're not even the best sea cucumbers. I think the biggest thing holding them back is a lack of information. Research is usually behind on invertebrates, and even further behind on deep sea life. I bet they're great migrators, but we have no info on that. For now, they're a very cute, tall, gummy version of a typical sea cucumber.