Zebrafish can recognize microplastics as inedible materials: Quantitative evidence of ingestion behavior.

This study investigated the ingestion behavior of zebrafish exposed to microplastic particles (MPs) at different concentrations, presented alone or in a mix with food particles. Zebrafish showed spitting behavior after ingesting micro-sized (247.5 μm) polyethylene particles (i.e., MPs), with prey-capture time increasing when food and MPs were supplied simultaneously. Fish were compelled to ingest MPs with food, and the accumulation percentage (ingested particles/supplied particles) was quantified as 0.5 to 9.4% with increasing food volume. However, the accumulation percentage was determined as 0.0 to 1.0% under exposure to MPs only, and as 3.8 to 4.3% at high MP concentrations when the food concentration was fixed. Overall, these results demonstrate that small freshwater organisms can recognize that MPs are not food items. Under laboratory conditions, zebrafish rarely discriminate between food and MPs when both are presented together, and the indiscriminate feeding behavior becomes clearer as more food is available.