Plastic litter in the sea makes hermit crabs “excited”

Ocean plastic has surprising effects on hermit crabs, says a new study.

Valery Sharifulin TASS via Getty Images

Ocean pollution has many consequences for marine life, including the “excitement” of hermit crabs.

Low levels of a common plastic additive called oleamide accelerate the crabs’ breathing rate, suggesting excitement and attraction to the material, according to a study published Tuesday in the Marine Pollution Bulletin. This may sound like a lot of fun to the crabs, but it’s another example of marine plastic destroying ecosystems and wildlife. Earlier this month, a separate study detailed the significant and heartbreaking damage that all of the plastic we throw in the ocean does to baby turtles.

Oleamide bears a striking resemblance to oleic acid, a chemical released when invertebrates called arthropods break down. The additive confuses the hermit crabs, says Paula Schirrmacher, a PhD student at the UK University of Hull who studies the effects of climate change and plastic on the small crustaceans.

“As scavengers, hermit crabs can incorrectly identify oleamide as a food source,” Schirrmacher said in a statement. “This research shows that additive washout can play a significant role in the attraction of marine life to plastic.” Oleamide in particular has the opposite effect on humans – some take the organic compound as a sleep aid.

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It’s easy to joke about happy hermit crabs here, but the University of Hull study highlights a sobering reality. According to the International Union for Conservation of Nature, at least 8 million tons of plastic end up in our oceans annually, and plastic makes up 80% of marine litter from surface waters to deep-sea sediments.

To study the reaction of marine animals to the smells emitted by plastic, the team collected 40 crabs off the coast of Yorkshire, England, and transported them to university aquariums. There, they measured the creatures’ respiration after injecting oleamide into their seawater habitats. “Our study shows that oleamide attracts hermit crabs,” said Schirrmacher, whose research focuses on how climate change can alter the chemical signals that aquatic life rely on to find their way around their environment.

“The potential of the wide variety of plastic additives to mimic natural infochemicals for a wide variety of species is a complex problem that urgently requires further investigation in order to initiate containment measures,” the study said.

Research by another team last year found that plastics impaired hermit crabs’ perception and impaired their ability to select the best shell and penetrate to protect their fragile exoskeletons.

In more optimistic news from ocean plastic Samsung announced on Wednesday that it is considering making phones from recycled marine plastic as part of its commitment to sustainability. The electronics giant is the latest big tech company to take on a stronger pro-planet pledge.


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Correction, August 13th: An earlier version of this story, based on University of Hull press materials, suggested that oleamide sexually aroused cancers. The university has changed its materials to exclude any connection with sexual response.

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