Things can get pretty hairy down at the bottom of the sea.
Crabs, for instance.
Not hairy as in scary. Hairy as in hirsute.
Scientists – marine biologists from the Monterey Bay Aquarium Research Institute in Moss Landing – have discovered a new species of crabs that they've named “hirsuta” because of their very hairy legs.
The crabs are also blind, smelly and endowed with many intriguing traits that set them apart from any other crabs that anyone has ever seen.
In fact, researchers believe that what they found isn't just a new species, or even just a new genus, but a whole new family of crabs.
Scientists first laid eyes on these creatures a year ago when they were snooping around the ocean floor about 900 miles south of Easter Island and more than a mile below the Pacific Ocean's surface.
Which explains why nobody had ever run across them before.
“This is the farthest south that any human-occupied submersible vehicle has ever gone,” said Joe Jones of MBARI, who was one of the humans who occupied the submersible vehicle Alvin during the expedition.
Geological surveys had predicted they would find vents in the area, which they did. Finding the hairy crabs was a lucky bonus.
“The Alvin has a very small window to look out of, about 4 inches in diameter,” Jones said. “You get a very narrow view of what's down there.”
And yet, on any one dive, researchers saw between five and 10 of the crabs – which seems to imply that the place might be crawling with them.
“As soon as we went a little farther north, though, we didn't see them any more,” Jones said. “We might have been on the edge of their distribution.”
Mussel eaters
A typical dive lasted seven or eight hours. “You're in this little sphere, it's really cold, and you really have to use the bathroom,” Jones said. “But you have to put all that aside and do your job.”
Alvin holds a pilot and two researchers. When the researchers see something they want to collect, the pilot uses a slurp gun to vacuum up the specimen.
But first he has to set Alvin down on the ocean floor, and that can have unfortunate consequences for any animals it happens to land on. Unfortunate consequences for mussels, however, might be fortuitous for hairy crabs.
“We saw them getting little pieces of mussels that got broken,” Jones said.
That provided one of the few facts that researchers know about hairy crabs: They can eat the tissue of other animals.
But researchers speculate that the crabs may also eat certain bacteria. At least, large colonies of bacteria live on the crabs' hairs, and it's possible that the crabs grow these colonies for food.
Researchers saw crabs stretching their claws over the outskirts of vents, perhaps because the bacteria thrive in the warm, gaseous water coming up there.
“The crabs could graze off the bacteria,” Jones said. But that's just one hypothesis. “Really, it's sort of a mystery what they do.”
Crab goddess
Much about the crabs is a mystery, but their bad smell is perfectly understandable. The water coming from hydrothermal vents is full of hydrogen sulfide, which smells like rotten eggs.
“Any animal that lives around the vents usually smells pretty foul,” Jones said. “Everything we bring up smells bad. Pretty soon the whole ship smells bad.”
The researchers only brought up one hairy crab, a male that didn't survive. Hairy crabs live under about 7,200 feet of water, or about 220 atmospheres of pressure. So coming to the surface gave him the crab equivalent of a fatal case of the bends.
In a way, though, the crab, about 6 inches long, has become immortal because he's now a “holotype” – the single specimen used to describe his kind.
But from looking at video of the dive, Jones said, “It turns out he's a small one. It looks like we got a baby.”
The crab is named Kiwa hirsuta, for the Polynesian goddess of shellfish. Its family name is Kiwaidae.
More affectionately, the hairy crab is called the Yeti crab, after the hairy abominable snowman of the Himalayas.
