(CNN) More than half a million hermit crabs have been killed after becoming trapped by plastic pollution on two remote islands, a new study from the University of Tasmania found.

Hermit crabs with Cocos Island plastic debris.

Research teams estimated that about 508,000 of the crustaceans have been killed in the Cocos (Keeling) Islands in the Indian Ocean and about 61,000 on Henderson Island in the Pacific after getting stuck in debris such as plastic bottles, which researchers said served as "deadly traps."

Hermit crabs do not have shells of their own, and instead use empty shells or hollow objects to shelter and protect their bodies.

Dr Lavers found more than 500,000 Cocos Island hermit crabs in discarded plastic buckets.

"When we were surveying debris on the islands, I was struck by how many open plastic containers contained hermit crabs, both dead and alive," Dr Jennifer Lavers, who led the study, said in a statement.

The study, led by the Institute for Marine and Antarctic Studies (IMAS) at the University of Tasmania, found that discarded plastic created a "physical barrier" for wildlife attempting to navigate their surroundings and acted as a trap for the crabs.

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