Range: Atlantic, Pacific, and India oceans

Habitat: 650 feet to over 3.7 miles (200-6,000m) deep

Size: 6 inches (15cm) long

Diet: Detritus 

Threats: Unknown

Lifespan: Unknown

Transcript:

Today on Animal Fact Files we’re discussing swimming sea cucumbers. Many sea cucumbers are believed to have the ability to swim even just a little, but there is a family of deep sea dwelling sea cucumbers that are specifically known as the swimming sea cucumbers. On top of that, at least one member of this family is considered the only known pelagic echinoderm! 

All sea cucumbers are echinoderms like sea stars and sea urchins. Most echinoderms, sea cucumbers included, are benthic creatures meaning they spend their lives on the bottom of the sea floor. The swimming sea cucumbers, however, are benthopelagic meaning they spend some of their time above the seafloor in search of food. One species is fully pelagic which means these animals spend their lives suspended in the water column! That would be like a sea star that swims for its entire life!

Swimming sea cucumbers look different from typical sea cucumbers. They're gelatinous and come equipped with twelve to twenty tentacles. Some even describe them as jellyfish-like in appearance. They can reach about six inches (15cm) in length and very little is known about them because they live from 650 to over 3.7 miles (200 to over 6000 meters) below the ocean's surface. While their reproductive habits are unknown, some consider swimming sea cucumbers neotenic in appearance meaning they retain characteristics of their juvenile stage in their adult form.

Unlike some typical sea cucumbers, it's believed that members of this family do not eviscerate their gut when faced with danger. These invertebrates likely eat detritus in the form of marine snow which is organic material, like waste, shed skins, and even corpses, that float down to the abyss from the waters above. Fully pelagic sea cucumbers have a funnel-like shape and swim with their mouth facing upwards to catch the food that falls from above.

So far, swimming sea cucumbers have been found in temperate and tropical areas of the Pacific, Atlantic, and India oceans. Like benthic sea cucumbers, such as sea pigs, who often gather in large groups on the ocean's floor, swimming sea cucumbers have also been seen in large groupings. 

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