Yeti crab grows its own food

By ED YONG - NATURE
Added: Sun, 04 Dec 2011 19:08:08 UTC

In the deep ocean off the coast of Costa Rica, scientists have found a species of crab that cultivates gardens of bacteria on its claws, then eats them.

The yeti crab — so-called because of the hair-like bristles that cover its arms — is only the second of its family to be discovered. The first — an even hairier species called Kiwa hirsuta — was found in 2005 near Easter Island.

Andrew Thurber, a marine ecologist now at Oregon State University in Corvallis, identified the second species a year later. “It was a big surprise,” he says. “There’s a tonne of them, they’re not small, and they’re six hours off a major port in Costa Rica.”

Writing in PLoS ONE this week, Thurber named the crab Kiwa puravida, after a common Costa Rican saying that means 'pure life'.

“Those of us who work in the deep sea expect to discover a strange new species every time we dive,” says Cindy Van Dover, a marine ecologist at Duke University Marine Laboratory in Beaufort, North Carolina. “Kiwa puravida doesn't disappoint. The original yeti crab was charismatic. This one is even more so.“

Ocean waves Thurber had not set out to discover species. He was part of a geological research cruise off the coast of Costa Rica, which aimed to study methane seeps — sites on the ocean floor that belch out methane and hydrogen sulphide gas. While exploring the seep in a submersible, pilot Gavin Eppard noticed the 9-centimetre crabs waving their claws over active seeps, and collected one. “He came up and just handed me this new species,” says Thurber.

The bristles that cover the crab’s claws and body are coated in gardens of symbiotic bacteria, which derive energy from the inorganic gases of the seeps. The crab eats the bacteria, using comb-like mouthparts to harvest them from its bristles.

The bacteria in K. puravida gardens are closely related to species that live in other cold seeps and hot hydrothermal vents all over the world. “It looks like the bacteria may use the seeps as stepping stones, to create this global connected population that consumes the energy coming out of seeps and vents,” says Thurber.