Creature Feature: Jeweled Anemone Hermit Crab (Dardanus gemmatus)

Photography by John Cooney

Today we are going to talk about a marine creature that is seriously resourceful when it comes to real estate:  the hermit crab!  You may already know that hermit crabs are well known swapping their shell homes for newer, bigger ones.  Like all crabs, the hermit crab possesses an exoskeleton that protects their body and maintains their form. However, hermit crabs take self-protection one step further by finding snail shells and coil their body inside, protecting their softer body parts from predators and environmental elements. When they grow too large for their shell home they will crawl out and find a new snail shell that fits perfectly. Anemone hermit crabs go one step further to make their home safe.

In past posts we have talked a lot about symbiosis. Anemone hermit crabs have a mutualistic relationship, which you will remember is where both organisms benefit. Carlie Cooney, MSI’s Land Program Manger recently was able to view a jeweled anemone hermit (also known as Dardanus gemmatus) while on a dive trip at Garden Eel Cove outside the Kona airport. Carlie’s cool fact about these accessorizing little crabs is that they will grab small anemones and attach them to their shell. Not just any old anemone will do – even when moving to a new shell, the crab makes sure to transfer the same anemone to the new location. There are typically two species of anemones associated with the jeweled hermit crab, Calliactis polypus and Anthothoe sp.

Jeweled anemone hermit crabs benefit by having extra protection due to the stinging anemone tentacles.  The anemones also can be placed on top of cracks or weak spots in the hermit crab’s shell.  Plus, anemones make for amazing camouflage among the rocks and corals. In return the sea anemone gets scraps from the food that the hermit eats and gets to piggyback to areas that are productive in nutrients. Anemones aren’t the only ones hitching a ride.  The jeweled hermit crab will also carry flatworms and amphipods, unwittingly housing an entire traveling community on its back!

References:

Edited by KC O’Shea

Photography by John Cooney https://www.flickr.com/photos/jmtb02/sets/72157647477618880/

http://www.hawaiianatolls.org/research/CoML/features/anemonecrabs.php

http://www.nrcresearchpress.com/doi/abs/10.1139/z70-056#.VC6rgfldUsc