'Yeti' Crab's Strange Body Suits Its Hellish Habitat
The white, blind and hairy yeti crab lives near hydrothermal vents, where boiling water spews from the earth's center.
What's white and blind and hairy all over? A yeti, of course! Or, in this case, a yeti crab - a marine creature that lives near the thermal vents in the ocean floor where hot water gushes into the sea.
There are three known species of yeti crabs, and now, in a new paper, scientists have described the characteristics of one of these species – Kiwa tyleri - for the first time. K. tyleri is the only species of yeti crab known to reside in the Southern Ocean, off Antarctica.
Researchers first photographed this deep-sea animal in 2010 using a remotely operated submersible vehicle (ROV). But the ROV did more than snap a few pictures of the furry crabs (some of which you can see here); it also vacuumed up a few specimens from about 8,500 feet (2,600 meters) beneath the Southern Ocean's icy surface, for further study. [In Images: The Amazing World of Antarctic Yeti Crabs]
Since then, researchers have studied the specimens using genetic sequencing and computed tomography (CT) scanning. Their description of the somewhat strange morphology of the yeti crab is published today (June 24) in the journal PLOS ONE.
Cramped quarters Many of the yeti crab's distinctive features - like its stark white coloring and its "hairy" body - are the creature's adaptations to its habitat, the researchers said. K. tyleri dwells in a "thermal envelope" of just a few square meters, where the water is just the right temperature, said Sven Thatje, lead author of the report and associate professor of marine evolutionary ecology at the University of Southampton in England.
"They're literally, in places, heaped up upon each other," Alex Rogers, a professor of zoology at Oxford University who led the expedition to the East Scotia Ridge, told Live Science in 2012. Photographs taken by Rogers' team show 600 crabs per square meter.
The reason for the crabs' tiny living quarters is simple: The water just outside their cozy home is very cold, Thatje told Live Science in an email. Water temperatures at that depth of the Southern Ocean typically fluctuate between about 30 and 33 F (minus 1.3 to 0.5 C).
"Crabs and lobsters are very rare in Antarctic/Southern Ocean waters because of the unusually low seawater temperatures," Thatje said. "A physiological limit to maintaining activities required for survival (ventilation, molting, mating) appears to exist at around 0.5 degrees C [32.9 degrees F]."
But some crabs do brave the icy waters away from the vents. Female yeti crabs leave the vents to brood their eggs, which researchers believe need cooler water to develop. The eggs would also be unlikely to survive so close to the hydrothermal vents' sulfur-rich emissions, Thatje said. But these mama yeti crabs have a thankless job: Once they are done brooding, they usually die, Thatje said.
"Females that move off-site do not feed; in fact, they starve," said Thatje, who hypothesizes that once the females leave the vents, they aren't strong enough to fight their way back into the crustacean melee.
Strange diet Yeti crabs survive by growing their own food, in a sense. The distinctive "hair" on their bodies that gives them their name is scientifically known as setae, and serves as a "garden" where the yeti crabs' favorite food - bacteria - grow.
Unlike Kiwa puravida – the yeti crab found near hydrothermal vents off the coast of Costa Rica that has setae only on its appendages - the Antarctic yeti crab also has setae along the underside of its body. The appearance of this "chest hair" led scientists to nickname Kiwa tyleri the "Hoff crab" after "Baywatch" actor David Hasselhoff, who (as you may recall) has a hairy chest. [From Blobfish to 'Adorable Octopus': 9 Animals with Perfect Names]
This difference in setae between the Antarctic yeti craband its two closest relatives, Kiwa puravida and K. hirsute (which inhabits the waters south of Easter Island, along the Pacific-Antarctic Ridge), is "remarkable," Thatje said. It's likely that the Hoff crabs' hairy chests are an adaptation. Their luxurious setae allow the Hoff crab to not only grow its own bacteria, but also swipe up bacteria that grow on the vent chimneys.
Thatje noted another adaptation that is particular to Kiwa tyleri: The crab has "spikes" on the end of its legs that allow it to climb steep surfaces. "This is a significant advance in its evolution, and differentiates it from the other known yeti crabs, which clearly do not possess the ability to climb vent chimneys," he said.
Although Thatje and his colleagues have shed light on some of the mysteries surrounding the elusive yeti crab, many questions remain. Further research is needed to understand how these heat-loving crabs came to colonize two vent systems that are separated by miles of frigid water, and how the yeti crab larvae make their way from the frigid depths of the Southern Sea to the cozy chimneys they eventually call home.
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This is a male yeti crab.
Jan. 3, 2012 --
Whole communities of previously unknown species thrive around deep-sea hydrothermal vents off the coast of Antarctica. A team of researchers led by the University of Oxford, University of Southampton and British Antarctic Survey used a Remotely Operated Vehicle (ROV) to film and bring back samples from the depths at two locations. "What we didn't find is almost as surprising as what we did," said team leader Alex Rogers of Oxford University's Department of Zoology in a press release. "Many animals such as tubeworms, vent mussels, vent crabs, and vent shrimps, found in hydrothermal vents in the Pacific, Atlantic, and Indian Oceans, simply weren't there." The Actinostolid anemones and stalked vent barnacles (cf. Vulcanolepas) pictured here clinging to a vent were some of the dominant animals at the more southern location, dubbed E9, at approximately 60 degrees south latitude and 2,400 meters (7,900 feet) deep.
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Black Smoker Vent
Black smokers are high intensity vents that belch out water and chemicals at up to 382.8 degrees C. The chemicals the vents release form the base of the local food chain while the heat sustains lifeforms that would otherwise freeze in the deep sea. "Hydrothermal vents are home to animals found nowhere else on the planet that get their energy not from the Sun but from breaking down chemicals, such as hydrogen sulphide," said Rogers. These Antarctic vents are legally protected by the Convention on the Conservation of Antarctic Marine Living Resources and the Antarctic Treaty, but deep sea vents further north may be threatened by deep-sea mining, warned Steven Chown of Stellenbosch University in a primer on hydrothermal vents published in the journal PloS One along with the findings of Rogers' team.
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One of the new species found on this expedition was a new species of yeti crab (Kiwa n. sp.) similar to another species Kiwa hirsuta. Genetic evidence suggests that the crabs diverged from a common ancestor approximately 12.2 million years ago. The yeti crabs were found at both locations E9 and the more northern E2, at 56 degrees south latitude and 2,600 meters deep.
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Crabs and Snails and Spiders, Oh My!
A yeti crab crawls over a groups previously unknown snail-like Peltospiroid gastropods while anemones sway in the current. Can you find the Pycnogonid sea spider hiding in the bottom left of the photo?
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A variety of sea anemones were found around the Antarctic vents. This large specimen clings to the side of one of the vents. Sea anemones are predators related to coral and jellyfish. Most use venomous tentacles to snag prey and drag it to their waiting maw. The venom also keeps predators at bay.
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Isis the ROV
This Remotely Operated Vehicle, named Isis, was lowered from the research vessel RRS James Cook. Isis sent back video of her journey and collected animals using both a scoop and a suction device. The samples were then dissected and analyzed to determine if they were new species. Another deep sea probe, the Seabird +911 CTD, sampled the water and analyzed the flow from the vents.
ROV Mission Control
The ROV was controlled from this video screen lined room aboard the research vessel.
Isis brought back this cross-section of a black smoker chimney to the surface. The chimneys build up due to volcanic activity which super-heats sea water which then jets back into the ocean. The dissolved minerals and other chemicals in the scalding water build up and form tubes. The researchers found black smoker chimneys up to 15 meters (49 feet) tall at the Antarctic sites.
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Although it looks like a flower, the sea lily, or crinoid, is actually an animal from the phylum Echinodermata. This one was photographed at the E9 site, near a collapsed lava dome known as the Devil's Punchbowl. The crinoid is an ancient class of animal first appearing in the fossil record during the Ordovacian Period, which occurred between 488.3 to 443.7 million years ago.
Another predator dining around the vents was a newly-discovered species of stichasterid sea star. The seven-armed star made a meal of yeti crabs and stalked barnacles while the scientists watched. Little else is known about this mysterious denizen of the deep. Sea stars are members of the phylum echinodermata, just like the sea lily. They occur in every ocean and are famous for their ability to regenerate their arms.
The sea stars fed on another newly discovered species of stalked barnacle. The barnacles of the genus Vulcanolepas, were genetically distinct from a similar species, V. Osheai, found on other hydrothermal vents. Stalked barnacles are filter feeding crustaceans.
An unknown species of octopus was found at E9. The scientists know little about it, besides that it exists.
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Yeti Crab Convention
Hardly a rarity, the yeti crabs covered the ground in some areas. The crabs are believed to be omnivores, feeding on the filamentous bacteria that feeds on the vents' chemical soup as well as the mussels and perhaps other animals.
Very Deep Sea Fishing
Few fish were found in the Antarctic vent ecosystem. But the ROV did manage to catch these Zoarcid fish in a baited trap.
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