Discover in the depths: sea cucumbers that live the life of jellyfish | Marine life

WWandering in the deep sea is a transparent creature that looks like a jellyfish, but in fact it is something else entirely. Pelagothuria natatrixmeaning the sea cucumber that swims, belongs to a group of animals that are famous for lying on the sea floor like giant rubber worms.

Pelagothuria: a species of sea cucumber spotted while diving in the deep sea – video

This sea cucumber was first named in the late 19th century, but for a long time it was known only from a few rusty specimens that grew up in scientific trawls. “It’s so fragile, it’s kind of intangible,” says Chris Mah, a biologist at the Smithsonian Institution in Washington, D.C. “The fact that it is gelatinous makes it very difficult to study.”

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The ocean is one of the last wild spaces in the world. It teems with fascinating species that sometimes seem to border on absurdity, from fish that peer through the translucent heads to golden snails with iron armor. We know more about deep space than the deep oceans, and science is just beginning to scratch the surface of the rich diversity of life in the depths.

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In 2014, Mah sparked what he described as a species rediscovery when he was searching a database of deep-sea images and spotted a parachute-like parachute. Pelagothoria They are incorrectly classified as jellyfish. Until then, he says, few scientists were aware of this species. Mah’s vision encouraged others to look for her during deep-sea surveys.

three years later, team of scientists Working in the Pacific Ocean got a wonderful view of these jossamer creatures in their natural habitat. While working on the research vessel Okeanos Explorer, the team watched video footage of Pelagothoria Launch in real time from a deep-diving robot.

During nine dives, between American Samoa and Hawaii, they spotted nearly 100 sea cucumbers swimming at depths ranging from 196 to 4,440 meters and often in areas of very low oxygen in seawater. Mah suggests that this could be PelagothoriaA tactic to avoid predators who are more hungry for oxygen and can suffocate easily.

Pelagothuria, a swimming sea cucumber that looks like a jellyfish
Pelagothuria natatrix was first named in 1893. Photo: NOAA/OER

How Pelagothoria Surviving in these difficult conditions remains a mystery, but it likely has something to do with his gelatinous body. Many animals that live in the deep sea have bodies made up mostly of water with a small amount of collagen mixed into them. This gelatinous substance requires little energy to make and maintain, and is therefore ideal for animals that live in the depths where food is often scarce. Gel-based animals are also buoyant by nature, so they don’t need to waste precious energy and aggressively swim with oxygen to stay afloat; They can only drift.

Among the approximately 1,200 species of sea cucumber, Pelagothoria He is the only one known to spend most of his time swimming. He uses the web around his mouth to propel himself through the water column.

Many other sea cucumber species are occasional swimmers. “They live on the bottom, but they can swim when they want to,” Mah says. The approach of a predatory starfish can move sedentary sea cucumbers into action. Even a few seconds of awkward swimming can be enough to escape.

This could be how Pelagothoria The ancestors started, then evolved to become better and better swimmers until they adopted the jellyfish lifestyle full time. It’s a case of convergent evolution where distantly related organisms – in this case sea cucumbers and jellyfish – have been able to solve challenges with a similar result.

“The gelatinous lifestyle is definitely something you see a lot in middle water animals,” Mah says. “It’s such a common adaptation that every organism has its own story about how it got there.”

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