Can Fish Escape the Evolutionary Trap Induced by Microplastics?

Microplastic (MP) ingestion acts as an evolutionary trap with various ecological consequences. Cues that lead animals to respond differently to MPs are key factors driving MP ingestion, yet they remain poorly understood. Here, we quantified the susceptibility of three fish species to different types of MPs across different social contexts. Our results showed that bass were more attracted to MPs that resembled food visually, whereas carp tended to select MPs that shared olfactory cues with food. Goldfish relied more on oral processing to make foraging decisions on MPs. Structural differences in the oropharynx supported these discriminated oral processes. Enlarged group size and fasting time altered the foraging behaviors of MPs of goldfish and bass, both of which were suction-feeding species. Such behavioral changes, regardless of whether fish ultimately ingested or rejected MPs, could pose indirect costs to fish. However, changed group sizes and fasting times did not affect the intake of MPs by the filter-feeding carp. We also proposed four pathways causing the MP-induced evolutionary trap and discussed the potential of fish to escape this trap. Our results contribute to experimental and theoretical understanding of the ecological risks posed by MPs to aquatic species.