A new study published in April 2020 found that exposure to microplastic can disrupt hermit crabs’ ability to choose the best shell for them.

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At a Glance

A new study found that exposure to microplastic can disrupt hermit crabs’ ability to choose the best shell for them—meaning, it impacts their cognitive function. The term "cognition" can be broken down to mean the gathering, processing and use of information in decision making.

It turns out plastic is really, really bad for hermit crabs' general functioning, and could also be really, really bad for other aquatic wildlife, too.

A new study found that exposure to microplastic can disrupt hermit crabs’ ability to choose the best shell for them— meaning, it impacts their cognitive function.

The study was designed to address whether microplastic exposure impacts the essential survival behaviours of hermit crabs when contacting, investigating and entering an optimal shell. The line of research was inspired by recent research on velvet swimming crabs, which revealed that ingested microplastics finds its way to their brain tissue, explained Andrew Crump, the lead author of the study. “No-one had tested how this might impact behaviour,” explained Crump, a PhD student with the School of Biological Sciences at Queen's University Belfast.

Scientists are only beginning to study the negative impacts of microplastics — pieces of plastic that are roughly a quarter inch or smaller. Studies reveal that and that it's being found in the bodies of living creatures from to to .

While there is a growing body of research into the effects of microplastic on aquatic mammals (the impacts include feeding patterns, stunted growth and reproduction), there is still not much research into the specific effects of microplastic on animal behavior and cognition.

“There are only a very limited number of studies that have investigated effects of microplastic exposure on animal behaviour and these findings from our initial study highlight the need for more research including additional behaviours and species,” Dr. Gareth Arnott, co-author of the new research from Queen’s University Belfast, told weather.com.

As was , the research team kept 64 female hermit crabs in tanks. After five days, they removed the hermit crabs from their shells and gave them new, suboptimal shells that were roughly half the ideal weight for each crab. Thirty five hermit crabs were exposed to microplastic, and 29 were not.

After two hours in their new shells, each crab was then put into a deep dish of seawater and with another shell— this time a perfect shell.

The 35 hermit crabs, scientifically known as Pagurus bernhardus, who were exposed to the microplastic showed impaired shell selection. They took longer to go explore and evaluate the new shell, and fewer hermit crabs explored at all. Only 10 made contact with the optimal shell, and only nine moved out of their too-light shells.

Those that were not exposed to microplastic were faster and more inclined to explore the new shell. A total of 21 of those crabs moved into the optimal shells.

This suggests exposure to microplastics affects the shell selection behaviour of hermit crabs, the team say, indicating that pollution could be affecting cognition. The results, according to study author Crump, “indicate that microplastics impair cognition, [and disrupt] an essential survival behaviour in hermit crabs.”

The term "cognition" can be broken down to mean “the gathering, processing and use of information in decision making,” explained Dr. Arnott.

“We know that shell selection behaviour in hermit crabs involves gathering information about shell quality, making assessments and decisions,” Garreth told weather.com. “Therefore, it is a nice system to study shell selection as a cognitive task and here ask if exposure to microplastic influenced that process.”

The extent of microplastics’ disruption to different aquatic species cognitive functioning hasn’t yet been explored in depth. This research team hopes to expand their research. Arnott’s current hypothesis is that the microplastic is “either disrupting [the hermit crabs’] feeding behaviour when exposed to microplastic or else that aspects of the microplastic were directly influencing their nervous system...However, this remains to be investigated.”

As Dr. Arnott emphasized, “there are only a very limited number of studies that have investigated effects of microplastic exposure on animal behaviour and these findings from our initial study highlight the need for more research including additional behaviours and species.”