Yeti crabs look like they’re wearing fuzzy fur coats, but they’re actually covered with bacteria and dense bristles called setae, which are used to help farm the bacteria for sustenance. A new yeti crab has just been discovered living in densely packed groups on hydrothermal vents off Antarctica – an incredibly unique warm-water refuge in deep polar waters. The new species is described in PLoS ONE this week.
Hydrothermal vent systems on the East Scotia Ridge in the Southern Ocean are some of the most isolating environments known: The temperature changes at these sites are insanely steep. Water spewing out of so-called black smokers can reach 380 degrees Celsius (716 °F). Lower structures along the chimney vents themselves can be about 25 degrees Celsius (77 °F), and the polar waters surrounding all this are a frigid zero degrees Celsius (32 °F), sometimes colder.
Now, meet Kiwa tyleri, a squat, eyeless lobster that spends most of its life trapped within the warm-water environment of a single vent chimney. After all, it can’t just walk over to other hydrothermal vent sites because of the permanently low temperatures of the polar waters in between. A female carrying eggs, however, will venture away from these chimneys to release her larvae into the surrounding deep sea. Her babies wouldn’t survive the warmer temperatures where the adults thrive.
A team led by University of Southampton’s Sven Thatje discovered the new species, which they named after a deep-sea biologist, when their remotely operated vehicle came upon two of these vent systems along the East Scotia Ridge. "It was immediately clear that we had something," he tells New Scientist. “There are piles of them all over."
Here’s an example of a Kiwa tyleri assemblage at "Black & White" chimney at the E9 vent field in the Southern Ocean. 2015 Thatje et al., PLoS ONE. Check out more awesome pictures!
“The species has adapted to this very limited sized habitat – of a few cubic meters in volume – by living in highly-packed densities and by relying on bacteria they grow on their fur-like setae for nutrition,” Thatje explains in a statement. So not only are these yeti crabs the dominant species at these sites, they also live at crazy high densities that exceed 700 individuals per square meter. They once counted 4,017 yeti crabs in a square meter.
Kiwa tyleri depend on bacteria for food. And in addition to farming bacteria, these yeti crabs also use their setae to harvest the dense bacterial mats that overgrow the surfaces of the vent chimneys where they live.
There are only two other members of the Kiwaidae family, and they both prefer low temperature environments and low-density aggregations of 10 specimens or less in a square meter. Kiwa puravida live around cold seeps off Costa Rica, and Kiwa hirsuta can be found on the periphery of hydrothermal vents on the Pacific-Antarctic Ridge in the southeastern Pacific Ocean. All three yeti crabs occur in the deep sea, about 1,000 to 2,400 meters (3,300 to 7,900 feet) below sea level, and they all farm and harbor bacteria of some kind.