Shell-shocked at finding new crab species
A NEW species of deep-water hermit crab – the green-eyed hermit crab – has been discovered by chance.
The creature is unique to South Africa’s West Coast.
UCT PhD candidate and researcher Jannes Landschoff said university alumnus Lara Atkinson made the discovery while she was conducting a survey for the Department of Agriculture, Forestry and Fisheries three years ago.
Atkinson was investigating Cape hake, and while doing so she stumbled on the new species. She sent it for identification and was surprised at her new discovery.
The green-eyed hermit crab is unique for its “living shell” – soft, polypy masses that are amalgams of sand and material created by colonies of sea anemones that live on its back.
Instead of a normal sea-like shell that most deep-water hermit crabs have, the green-eyed species has a pseudo-shell as it consists of the symbiotic relationship it has with anemones.
Sea anemones anchor themselves on the backs of these hermit crabs for shelter and simultaneously grow as the crab grows.
In addition to their green eyes, other unique features include biserial (two rows) gills and extreme sexual dimorphism. This means the male species grow a much larger right claw compared with females.
The crab measures around 70mm, and bears Atkinson’s name, Paragiopagurus atkinsonae. There is no indication why this species is restricted to this very small area of the West Coast.
Landschoff said there are between 2 000 to 3 000 of these crabs in the region.
“When you hold the hermit crab, it’s just organic material glued together with some sand.”
Landschoff and Rafael Lemaitre of the National Museum of Natural History at the Smithsonian Institution in the US recently described the new species in ZooKeys, a scientific journal covering zoological taxonomy, phylogeny and biogeography.
It is one of three hermit crabs that Landschoff is describing as new to science for his doctoral thesis.