Hermit Crabs Are Now Using Our Trash for Shells

Unlike snails or turtles, hermit crabs don’t have natural armor. Instead, they find and occupy empty seashells to protect their fragile exoskeletons. Their attraction to plastic waste could signal multiple things, the researchers explained. The animals may choose a trash shell because it offers better camouflage in a polluted environment, because it is lighter, or simply because it is available. Other potential reasons include sexual signaling when finding a mate or an odor cue (the species use the smell of dimethyl sulphide, which is emitted by dead hermit crabs, to find available shells; this same chemical is found in marine plastic).

The resourceful animals are known to fight over desirable homes, but it is not yet understood whether they’d do the same over the plastic version. “What we don’t know is how much the element of novelty might affect them, and whether the crabs will fight over artificial plastic shells,” Szulkin added.

A hermit crab uses a shot glass in place of a seashell for protection.

Photo: Luis Diaz Devesa/Getty Images

Plastic currently makes up 80% of all marine debris, according to the International Union for Conservation of Nature. Each year, 14 million tons of plastic finds its way into our oceans, which is extremely dangerous for marine species who ingest or get entangled in it. The paper’s authors are still trying to determine whether, in this case, the trash could prove useful to hermit crabs long-term. “Are artificial shells setting the scene for a novel evolutionary trajectory in hermit crabs,” they wrote, “or are they an ecological and evolutionary trap of the anthropocene?”

While further research is still needed, Mark Miodownik, a professor of materials and society at University College London, offered a silver lining and lesson for humans. Speaking with the BBC, he said, “Just like the hermit crabs, we should be reusing plastics much more, instead of discarding it.”

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