UCT researchers discover new species of crab

IT has green eyes, a girl’s name and, like other parapagurid species, piggybacks its tentacled lodgers around in a unique biological marriage called symbiosis. Meet Paragiopagurus atkinsonae, a new species of deep-water hermit crab found only in a tiny area off the West Coast of South Africa.

The tiny creature (it’s around 70mm long) bears the name of UCT alumnus Dr Lara Atkinson, the marine researcher who first noticed it, but goes by the common name “green-eyed hermit crab”.

UCT PhD candidate Jannes Landschoff and Rafael Lemaitre of the National Museum of Natural History at the Smithsonian Institution in the US described the new species in ZooKeys, a scientific journal.

It is one of three hermit crabs that Landschoff is describing as new to science for his doctoral thesis.

The story starts in a modestly sized area in the shallower deep waters (199m to 277m) off the West Coast.

Our deep waters teem with hermit crabs, as shown by the Department of Agriculture, Forestry and Fisheries’ surveys.

Atkinson is a researcher with the South African Environmental Observation Network. She was on board the RS Africana implementing their long-term invertebrate monitoring programme when the dense bounty of one trawl was being sorted during a three-week survey in 2013.

Hermit crabs of the Parapaguridae family usually account for a huge portion of the trawl. But that day she noticed something different. One of the tiny crustaceans was looking at her with green eyes. Curious, she sent it for identification.

Enter Landschoff and Lemaitre, the expert on hermit crabs. But such is the number of unidentified species arriving at his laboratory at the Smithsonian that his reaction to a new sample is often: “Oh my gosh! What is this?”

Landschoff remembers a stronger response when Lemaitre first encountered the green-eyed hermit crab.

They co-authored a detailed study and showed that they were indeed looking at a new species: the 25th in the genus Paragiopagurus Lemaitre, 1966, from the family Parapaguridae, one of six hermit-crab families.

This little hermit crab is a mottled orange with cream to white colouring.

Besides their green eyes, they’re distinguished by biserial gills, drastic sexual dimorphism, exhibited by the large right celiphed (claw) and, in males, the presence of specially shaped, unpaired second pleopods, which are modified as gonopods that hermit crabs probably use to pass on sperm during copulation.

As the hermit crab grows, its live “shell”, or carcinoecia, grows with it.

“They can reach incredible densities in offshore areas because they don’t need to find new homes,” Landschoff explained.

BESIDES THEIR GREEN EYES, THEY’RE DISTINGUISHED BY BISERIAL GILLS AND DRASTIC SEXUAL DIMORPHISM