These hermit crabs shack up inside living coral instead of mere shells

A tiny bit of pinkish cotton candy scurries its way along the sandy substrate. Other squishy-looking blobs rest until disturbed, perhaps by a sudden influx of sand or dirt, and then wriggle their way free—with the help of a worm that lives comfy cozy inside each globule.

During a survey looking for life on the seafloor of the Oshima Strait in southern Japan, ecologist Makoto Kato collected one of these specimens of walking coral, a group of species far more adventurous and mobile than its reef-dwelling relatives.

But back in the lab, he noticed that instead of the symbiotic worm he expected to find poking out of the coral, there was a small pincer. When Kato and his colleague, Momoko Igawa, opened the coral up, they found a slender hermit crab.=read more