Sea cucumbers bloat themselves to zoom around the ocean

Despite their slug-like reputation, these squishy creatures can actually zip along for miles on ocean currents.

Sea cucumbers are found on seafloors worldwide (this one, Cucumaria frondosa, is in Norway). New research shows that some of them don't just lay on the seafloor like a vegetable, though—they can make themselves buoyant and catch a ride on currents.

Sea cucumbers, long confined to the slow-moving category of marine critter, are actually high-speed travelers, new research reveals.

When they fancy a change of scene, the sea creatures balloon up and hitch a ride on ocean currents, floating and bouncing around like tumbleweeds of the sea.

Sea cucumbers (also dubbed sea slugs, because of their unhurried nature) were thought to be capable of swimming long distances only during their larval stage, like most bottom-dwelling sea creatures. After becoming adults and settling down, they either crawled, or—if a predator was lurking around—crawled slightly faster.

But it seems they've been hiding a far more efficient mode of transport. By flooding their bodies with water, they reduce their density until they’re buoyant, detaching from the floor and opening themselves up to the mercy of the sea. (And at least one, Enypniastes eximia or informally the “headless sea chicken,” has been spotted using winglike fins to swim.)

“They take up water from all the orifices they can, including through the anal opening,” says Annie Mercier, a marine biologist from Memorial University of Newfoundland in Canada and coauthor of the study, published January 12 in the Journal of Animal Ecology. The animal's respiratory system, which uses the anal opening to move water in and out of its body, sucks in water and becomes flooded. Some sea cucumbers then went bottoms-up, with the heavily dilated anus floating around to the top spot.

Mercier, who has been researching sea cucumbers since the 1980s, investigated a trail of...

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