Does microplastic exposure and sex influence shell selection and motivation in the common European hermit crab, Pagurus bernhardus?

Microplastics (<5 mm) are a threat to marine biodiversity however their effects on animal cognition and behaviour are unclear. We investigated whether microplastic exposure affects shell selection behaviour and motivation in the com-mon European hermit crab, Pagurus bernhardus. Subjects were maintained for 5 days in tanks containing either: poly-ethylene microplastic spheres (n = 40), or no plastic (n = 40). They were then placed in low-quality shells and presented with an alternative high-quality shell. When they first touched the high-quality shell, the hermit crabs were startled using visual and aural stimuli. We recorded the post-startle latency to re-contact the high-quality shell, quantifying motivation to explore and acquire a better shell. Plastic-exposed females were more likely to select the high-quality shell than control females. As hypothesised, female hermit crabs had longer initial contact latencies, star-tle durations, and shell entry latencies than males. We also found an interaction effect on shell investigation duration: females from the control treatment spent longer investigating the high-quality shell compared to males. This was ab-sent in the microplastic treatment with females behaving similar to males. This controlled study serves as a starting point to investigate the effects of microplastics and sex differences on behaviour when under predatory threat, and demonstrated sex dependent sensitivity to an environmental pollutant of global concern.

Automated summary

Microplastics pose a threat to marine biodiversity, but their impact on animal cognition and behavior remains unclear. A study on common European hermit crabs found that females exposed to microplastics were more likely to choose high-quality shells compared to control females. Additionally, females exhibited longer initial contact and startle durations compared to males. The study highlights the importance of investigating the effects of microplastics and gender differences on behavior when under predatory threat.