How did the chest-hair-farming Hoff crab evolve? Scientists solve mystery

This crab has come a long way to farm its own chest hair.

A team of Oxford University scientists has found that Hoff crabs are recent migrants from the Pacific Ocean, taking the Drake Passage between South America and Antarctica and scuttling to deep-sea vents in the Southern and Indian Oceans. They are believed to have split from their cousins, the hairy-clawed Yeti crabs, in making the long move.

Hoff crabs were discovered in 2010, some five years after the discovery of the Yeti crab. The two species are now believed to share a common ancestor that lived about 40 million years ago.

Hoff crabs, so named after shaggy-chested actor David Hasselhoff, had previously thought not to have moved much at all. Scientists had suggested that the unusual animals were living fossils, ancient crabs that had been forgotten deep beneath the sea.

The furry little crabs make their homes in some of Earth's most improbable environments, clinging to deep-sea volcanic vents that heat the water to 716 degrees Fahrenheit. There is no light there, and the water offers little oxygen, but lots of noxious chemicals, . 

To survive there, the Hoff crabs resort to inventive agriculture. These animal anomalies feed themselves by 'farming' bacteria in the hair on their chests. They then comb their hair with their mouth, like a tractor chugging through tracts of crops, and feast on the bacteria grown on their chest plantation. 

Still, despite that creative farming, the new research published in Proceedings of the Royal Society B suggests that the crabs are becoming increasingly vulnerable, as global warming alters the oxygen levels of our oceans. That change tips out of balance a delicate ecosystem in which the crabs survive: the crabs must get just close enough to the vents to farm their bacteria (which live off the vent’s chemicals) but also stay just far enough from the vents to source enough oxygen (which is not available to close to the vents) to breathe. Getting too close to the vents means getting boiled.

“The life of these charismatic crustaceans is a delicate balancing act,’ said Nicolai Roterman of Oxford University’s Department of Zoology, in a press release. “Their challenge is to position themselves close enough to the vents to thrive but not so close that they risk suffocating or getting cooked alive.” 

Scientists believe that a previous period of global warming about 55 million years ago lowered the oxygen levels around the vents to the point that all the animals there were killed off, to be replaced with this latest batch of resourceful animals, including the Hoff Crab.