Check out this new species of a hermit crab found off the coast of Japan, finding its new home by joining forces with a living coral that continues to grow!
This means that this crustacean known as Diogenes heteropsammicola, no longer needs to go on a life-long search for a bigger shell to live in, and can instead finally settle down. In fact, this crab is the first species to have ever been found to live within a “walking coral”, which is a free-living species of coral that grows as little lumps on the sea floor.
And while most hermit crabs have an asymmetric body to match the asymmetric shells they find and live in, the D. heteropsammicola has a perfectly symmetrical body that fits inside the coral with ease!
Circumstances like this, wherein half of a symbiotic relationship diversifies to include other organisms are actually rare, since this tends to require a high specialization or accommodation to include the other.
But lo and behold, this unique relationship between the crustacean and coral has worked out unexpectedly! The hermit crab fills the role of carrying the coral around the sea floor as it goes about its activities, and at the same time preventing the coral from being buried in the sediment.
On the other hand, the coral offers a unique service to the crab in that it provides a shelter and a home as it physically grows with the crab as time passes. In this way, the crustacean no longer needs to go on its never-ending search for bigger shells to live in as it ages.