For the 11th day of the Microbial Advent Calendar what about a fantastic winter themed monster? Ladies and Gentlemen, I present to you the mythical, the mysterious, the only one, the YETI crabs…
*Cough, Cough*
Unlike its (still) elusive homonym, the yeti crab is the informal name of a deep sea crab genus, the Kiwa. The first species was discovered in 2006 on a methane leakage (cold seep) near Costa Rica, since then at least two more species were discovered on hydrothermal vent sites. These hairy white crabs are clustering in densely packed colonies, up to 700 individuals per m², close to the methane or vent fluids where every individual appears to be involved in a constant dance. Indeed, when they are not fighting each other, they are waving their overgrown hairy claws in the water stream and because of this behaviour, they also are known as the dancing crabs.
But why are they doing this? Because of a symbiotic association with bacteria! The white hair present on the appendages and other setae of the crab are covered with a collection of bacteria organised either as single individuals or filaments. These bacteria are chemosynthetic, meaning they can use the reduce compounds (like methane or sulphur) present in the fluids from the cold seep or hydrothermal vents as energy and/or carbon sources. These bacteria are grown on the crab, then eaten by it using some comb-shaped claws.
In some way, these crabs are dancing farmers of the deep sea! Below you can even watch a youtube video from the National Geographic channel.
You can find more info about those guys in the following papers: here, here and here