Microplastics pollution is causing disruption and behavioural changes among hermit crab populations, researchers have claimed.


Hermit crabs require shells from snails for protection and to reproduce. The new research, authored by academics from Queen’s University Belfast and Liverpool John Moores University, found that exposure to microplastics left the crabs less likely to later touch or enter high-quality shells.

Lead researcher Dr Gareth Arnott, from Queen’s University, said exposure to microscopic particles of plastic in the water has a detrimental impact on the crabs. By impairing a crab's ability to gather and process information about its surroundings, the microplastics disrupted an essential survival behaviour.

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“Our research shows that exposure to microplastics can have important effects on animal behaviour. More specifically, in this case it had a detrimental effect on shell selection behaviour in hermit crabs,” he said.

“As this behaviour is vital for hermit crab survival and reproduction, there could be important long-term consequences.”

During their research, the academics divided hermit crabs between experimental tanks, half containing microplastics while the other half had no plastic.

After five days, the hermit crabs were moved into low-quality shells, but with alternative, higher-quality shells offering more protection available. The crabs that had been in the tank containing microplastics were less likely and slower to move to the better shells.

Dr Arnott added: “Our research shows for the first time how microplastics are disrupting and causing behavioural changes among the hermit crab population."

The exact mechanism by which this happens is unclear, but the authors of the study write that ingested microplastics can enter the brain in crabs, potentially impeding information-gathering, resource assessments, decision-making and behavioural responses.

“Hermit crabs are an important part of the ecosystem, responsible for ‘cleaning up’ the sea through eating up decomposed sea-life and bacteria," said Dr Arnott.

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“By providing a hard, mobile surface, hermit crabs are also walking wildlife gardens. They host over 100 invertebrate species – far more than live snails or non-living substrates.

“Additionally, commercially-valuable species prey on hermit crabs, such as cod, ling, and wolf-fish.

“With these findings of effects on animal behaviour, the microplastic pollution crisis is therefore threatening biodiversity more than is currently recognised so it is vital that we act now to tackle this issue before it becomes too late.”

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The research is published in Biology Letters.

Reader Q&A: How does plastic get into the oceans?

Asked by: Tamsin Nicholson, via email

Around 80 per cent of the plastic waste found in the oceans today originated inland. Littering, poor waste management and industrial activity can all allow plastic to enter the natural environment.

A significant proportion of this then blows into rivers and streams, which carry it into the ocean. This is particularly common in countries where waste infrastructure is lacking: an estimated two billion people worldwide don’t have access to solid waste collection.

On top of this, wastewater from our homes often contains tiny pieces of plastic, including microbeads from cosmetics (now banned in the UK) and fibres from polyester clothing. Tackling plastic pollution therefore requires individuals, governments and companies across the globe to work together to reduce plastic consumption and waste.

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Amy ArthurEditorial Assistant, BBC Science Focus

Amy is the Editorial Assistant at BBC Science Focus. Her BA degree specialised in science publishing and she has been working as a journalist since graduating in 2018. In 2020, Amy was named Editorial Assistant of the Year by the British Society of Magazine Editors. She looks after all things books, culture and media. Her interests range from natural history and wildlife, to women in STEM and accessibility tech.