Newly Discovered Hermit Crab Species Lives In ‘Walking Corals’

2017-09-29T09:33:51+00:00 September 29, 2017|

(Click to enlarge). A new hermit crab species, Diogenes heteropsammicola, has a symbiotic relationship with to reflect its relationship with the Heteropsammia coral genus. (Photo credit: Momoko Igawa)

Hermit crabs are well known for their ability to turn an empty shell into protective armour, but it seems that shells aren’t the only armour around. A new species of hermit crab that shelters in solitary corals has been discovered in southern Japan. Details of the discovery, made by scientists at Kyoto University, have just been published in the journal PLOS ONE.

(From Yahoo News / by Sara Mynott) — With bright red legs and brilliant white claws, the adult crab is just a few millimetres across but is capable of carrying coral bodies that are far larger. Named after the coral it carries, Diogenes heteropsammicola has a lot to gain from having a coral for a home.

Throughout their lives most hermit crabs shift from shell to shell to get a better fit, competing with other crabs to get the best deal. But for this particular species, there is no need. Its body sits safely curled up inside a cavity in the coral – a space that grows with the crab, so it never needs to find a new shelter. To add to that, the coral comes with a sting, protecting the crab from would-be predators, like starfish, larger crabs and octopus.

The crab certainly gets a good deal here, but what of the coral?

Not all corals are the reef-building kind. Solitary corals, like those inhabited by these crabs, are often found on shallow sandy seabeds. Such a lifestyle comes with the risk of being buried by sediment and overturned by strong currents. To combat this, some (known as walking corals) have evolved an incredible partnership with other creatures to shift them out of the sand and on to pastures new. Walking corals literally use other species to do their walking for them.

Until now, the key coral-shifting creatures we knew about were “sipunculans” – a type of marine worm that, in exchange for accommodation, would shuffle corals across the seafloor. Relationships like this are known as symbiotic and each partner, accordingly, is known to science as a symbiont.

It is very unusual for a symbiotic relationship to change and – if it does – the new partner is usually from a closely related species. This is because both symbionts are heavily dependent on each other. They are also highly specialised, which makes working with another partner difficult.

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