Dancing for food in the deep sea – NIWA scientist helps discover a new yeti crab off Costa Rica
The 'yeti crab' generated media attention worldwide when the first species was found around deep-sea hydrothermal vents off the Easter Islands at around 2200 m depth (Macpherson, Jones & Segonzac, 2005).
Only a single male specimen was collected then and since, and this was too precious for extensive tissue sampling to find out more about the organism, so many questions remained unanswered. A new family of squat lobsters, the Kiwaidae, had to be established to accommodate this strange, blind and furry-looking yeti crab, the appearance of which is also reflected in the scientific name, Kiwa hirsuta.
A second species, formally named Kiwa puravida, has now been described by Dr. Andrew Thurber (formerly at Scripps Institution of Oceanography, now at Oregon State University) and his collaborators, including Dr. Kareen Schnabel at NIWA, Wellington. This find is particularly interesting for a number of reasons:
- The new species was collected around cold seeps rather than hot vents. Although the animal communities that inhabit these types of environments are fuelled by similar processes involving chemosynthetic bacteria, it implies an historic habitat shift and probably indicates that there may be more undiscovered yeti crabs lurking in the deep.
- Underwater video footage of clusters of this species provided first insights into curious 'arm-waving' behaviour and subsequent observations of live specimens in laboratory conditions further led to the hypothesis that this species was 'farming' chemosynthetic bacteria on the thick aggregations of seta on its body and claws. The waving motion is thought to enhance exposure of the bacteria to the oxygen and nutrients dissolved in the water immediately adjacent to the cold seep, thus providing a good substrate and optimal growing conditions. Supporting evidence was provided by observations in a laboratory aquarium of a live specimen that appears to be transferring particles from the seta on the claws to the mouth (video of the yeti crabs).
- Because Kiwa puravida occurred in large numbers, several specimens were collected for further examination. Gut content, lipid and stable isotope analyses confirmed that the main food source indeed appears to be the chemosynthetic bacteria that abundantly grow on the thick 'fur' of the crab. In addition, close examination of the mouthparts revealed distinct modifications that act as combs, which very effectively remove the bacteria.
The paper concludes that this is the first clear evidence that crustaceans associated with either deep-sea vents or seeps actively harvest and utilise the chemosynthetic bacteria as their main food source. This study combined classical taxonomy with molecular, nutritional and observational evidence to provide us not only with an insight into a fascinating new species but also a compelling illustration of the complex interactions among organisms in the marine environment.
Kareen Schnabel, NIWA scientist and third author, explains the discovery in this interview.