The ‘Walking Dendro’ coral known as Heteropsammia or knuckle coral is one of the most unique solitary corals. Its association with a peanut worm in its base to help get around is well known but apparently we’re just beginning to learn of its powers of mobility.
As it turns out, in the shallow waters of Japan there is a very specialized hermit crab that can take over this role for walking Dendro corals. The newly minted hermit crab species is very different from typical hermits, especially in having very skinny legs, and quite prominent feathered antennae.
It’s one thing to have a single worm poking out of the base of Heteropsammia and Heterocyathus corals. But seeing this new species of hermit crab actually walking around wearing these solitary coral polyps like a backpack is a complete trip.
Symbiosis is a well known phenomenon in the natural world but symbiont shift, where one symbiont takes over for another, is very rare. Apparently, the researcher who described the new hermit crab, Diogenes heteropsammicola, goes on to discuss coral-crab associations in the fossil record.
There’s countless examples of crabs and hermit crabs living with corals and anemones, coral hermits who live inside stationary corals are well known, and staghorn hermits wear a shell covered with a kind of fire coral. But this is the first time we’ve seen a living, walking association between a hermit crab and a true Scleractinian coral. [PopSci]