Ocean Plastics

Hermit crab behaviour affected by microplastics

WRITTEN BY Oceanographic Staff

A new study found that microplastics impair the attacking as well as hermit crab defending behaviour, ultimately harming the crab’s shell selection assessment which is vital for their survival.

Today, microplastics can be found in marine ecosystems all over the world, from lakes to beaches and the open seas. The negative impacts on species digesting these microplastics are not yet fully understood. However, a new study, published in Royal Society Open Science, is trying to shed some light on the implications for hermit crabs by researching how their behaviour is affected when being exposed to microplastics.

Ultimately, the researchers behind the study found that microplastics impair the attacking as well as the defending behaviour of hermit crabs during shell fight contests. Furthermore, microplastics seem to impair the crab’s shell selection assessment; an essential behaviour for their survival. Hermit crabs rely on finding shells from marine snails to protect their soft abdomens and as they grow, they need to replace their old shells with larger specimens. One way to get hold of a larger shell is to fight another hermit crab with a favourable shell. During these fights, the ‘attacker’ tends to rap their shell against the ‘defender’s’ shell to evict the opponent.

The new study builds on research previously conducted by Queen’s University that found that hermit crabs that were exposed to microplastics ended up less likely touching or entering high-quality shells. The new study now reveals a more in-depth insight into the effects of microplastics on hermit crabs.

For the study, hermit crabs were put into two seperate tanks for five days; one tank was filled with a common microplastic pollutant, while the other didn’t contain any plastic. The findings: Plastic-exposed crabs had weaker attacking behaviour during fights and when defending their shells, they weren’t able to properly assess their attackers which made them give up their shell earlier.

Manus Cunningham from Queen’s University and one of the lead researchers on the paper, said: “These findings are hugely significant as they illustrate how both the information-gathering and shell evaluations were impaired when exposed to microplastics. Although 10 per cent of global plastic production ends up in the ocean, there is very limited research on how this can disrupt animal behaviour and cognition. This study shows how the microplastic pollution crisis is threatening biodiversity more than is currently recognised.” 

Hermit crabs are an important part of marine life and play a vital role in ecosystems through eating bacteria and decomposed sea-life. “These impacts on animal contests indicate that microplastics have broader deleterious effects on marine biota than currently recognized,” the study argues.

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Photography courtesy of Unsplash.

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