Range: Cosmopolitan 

Habitat: Seafloor

Size: Generally less than a foot (30 cm) long

Diet: Organic particles filtered from sand

Threats: Sea stars, fish, parasitic snails, and more

Lifespan: Unknown but likely less than a decade

Transcript:

Today on Animal Fact Files we’re discussing sweet potato sea cucumbers. Sweet potato sea cucumbers are also known as rat-tailed sea cucumbers, and they get both of these common names for how they look. All the members of this order have a unique, noticeable tail! Most sea cucumbers have rounded bums, but sweet potato sea cucumbers can have long, tapered tails reaching as long as half the length of their body! For these echinoderms, that's about eight inches (20 cm) on average, but they can nearly double that when they're fully stretched out! When they're disturbed, they puff up into a tight ball, making their body appear shorter and rounder.

There are two reasons this animal's name references food: one, they look like sweet potatoes; and, two, many of them live buried in the sand and mud, just like a growing potato! Sweet potato sea cucumbers, sometimes referred to as sweet sea potatoes, are benthic animals: they live on the bottom of the ocean. They can be found from shorelines down to the abyss, and they live in marine waters around the world! If they don't live on the seafloor then they burrow into it. Their burrows can reach more than a foot (30 cm) deep! From here, they stick their tentacles out and collect passing food. 

Like other sea cucumbers, sweet potatoes gather sand with their finger-like tentacles and ingest it. As the sand is digested, organic debris present there is sifted out and used as food. Whatever is left behind is pushed back out! Sea cucumbers look so puffy because they're often full of sand waiting to be released. Sweet sea potatoes, however, look different from some other sea cucumbers. They lack tube feet so their leathery skin is smooth and sometimes even shiny. Some observations suggest their tail feels more prickly than the rest of their body, and at least one species starts out gray in childhood but slowly turns red as it ages. 

It's not uncommon to find these animals living in groups at the bottom of the ocean numbering to about a dozen sea cucumbers in a small amount of space– think about the square footage of a single room in a house. When they're gathered in a group, it's easier for them to ensure their sperm and eggs more likely come in contact during spawning events. Like other sea cucumbers, sweet sea potatoes release their gametes into the ocean where they're fertilized externally. The eggs remain suspended in the water column until they hatch into planktonic larvae which eventually settle on the seafloor and metamorphose into adults. 

While gathering together is a great strategy for reproduction it can mean disaster if a predator shows up. Sweet potato sea cucumbers are predated by sea stars, fish, and other marine animals. There are also small, boring snails that drill holes into the cucumber's surface and consume their bodily fluids until they eventually perish. The life span of sweet potato sea cucumbers is undocumented, however, most of these animals live less than a decade in the wild.

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