Microplastics threaten survival of hermit crabs 

The common hermit crab's habitat has been negatively affected by the presence of microplastics. Pic: Paul Kay

New research at Queen’s University Belfast has highlighted the negative impact of microplastics on the behaviour and survival of hermit crabs.

Hermit crabs play an important role in balancing the marine ecosystem, with research revealing that microplastics are negatively affecting their behaviour, including their ability during shell fight contests, which are vital to their survival.

The research revealed that microplastics impair both the attacking and defending behaviour of hermit crabs, impeding their ability to secure the larger shell required for both their growth and survival.

The new study builds on previous research that showed hermit crabs were less likely to touch or enter shells when exposed to microplastics.

Published in Royal Society Open Science, the study provides a more in-depth insight into how the hermit crabs behaviour is impacted by microplastics.

There is a strong association between hermit crabs and their shelters or shells.

Hermit crabs play a vital role in are an important part of marine life and they recycle energy back into the ecosystem through eating-up decomposed sea life and bacteria.

As the hermit crab grows over the years, it will need to find a succession of larger and larger shells to replace the ones that have become too small through contests.

Vital protection

In such contests, the hermit crabs will fight a competitor to secure the shell that they favour. These shells are vital in protecting and enabling hermit crabs to grow, reproduce and survive.

The research involved keeping hermit crabs in two tanks: one which contained polyethylene sphere, which is a common microplastic pollutant and one without plastic, which acted as the control, for five days.

The team simulated the environment to encourage a hermit crab contest through placing pairs of hermit crabs in an arena and giving the larger crab a shell that was too small and the smaller crab a shell that was too big.

During the fights, plastic-exposed hermit crabs displayed weaker attacking behaviour than crabs that were not exposed to plastic.

Microplastics also reduced the ability of defending crabs to properly assess their attackers during contests and impaired their decisions.

One of the lead researchers on the paper, Manus Cunningham from Queen’s University, described the findings as “hugely significant” as they illustrate how both the information-gathering and shell evaluations were impaired when exposed to microplastics.

“Although 10% of global plastic production ends up in the ocean, there is very limited research on how this can disrupt animal behaviour and cognition,” said Manus Cunningham.

This study shows how the microplastic pollution crisis is threatening biodiversity more than is currently recognised.

Dr Gareth Arnott, the principal investigator of the project said: “This study provides an insight into the potential for microplastics to alter important aspects of animal behaviour that are critical for survival and reproduction.

“We need to further investigate how microplastics affect their behaviour and the consequences, armed with this knowledge to advocate for change to protect our ecosystem.”