The digestive system of a cricket pulverizes polyethylene microplastics

Abstract

Microplastics (MPs; <5 mm) are a growing concern and a poorly understood threat to biota. Despite a recent spike in research on MPs, most of this work has focused on marine systems, and less is known about interactions between terrestrial organisms. We used a generalist insect (a cricket; Gryllodes sigillatus) to examine whether individuals would ingest and physically degrade MPs in their food. We fed crickets a range of concentrations (0, 2.5, 5, and 10% w/w) of fluorescent MPs mixed into a standard diet and dissected the gut regions to isolate the MPs within. Comparing plastic content and fragment size within gut regions, we sought to identify whether and where crickets can fragment ingested MP particles. Given the digestive tract morphology of this species, we expected that the crickets would both ingest and egest the MPs. We also predicted that the MPs would be fragmented into smaller pieces during this digestive process. We found that G. sigillatus egested much smaller pieces than they ingested (likely into the nanoplastic range), and this fragmentation occurs early in the digestive process of this insect. These findings suggest that generalist insects can act as agents of plastic transformation in their environment if/when encountering MPs.