Integrating microplastics into thermal biology in an insect.

Microplastics (MPs) are small-sized (< 5 mm) bits of plastic present in all types of environments, including terrestrial ecosystems that are rapidly warming. Yet, the biological interplay between MPs and temperature is poorly understood in terrestrial animals. Here, we addressed three hypotheses to determine how: (1) temperature influences biological responses to MPs, (2) MPs influence thermal biology, and (3) temperature and MPs combine to influence the acquisition and allocation of resources. Specifically, we fed field crickets (Gryllus lineaticeps) different concentrations of nylon (polyamide) microfilaments while they were maintained at 23 °C, 28 °C, or 33 °C. Despite ingesting 2.5-fold more MPs, warmer individuals did not absorb more MPs into their bodies. Exposure to MPs increased investment into somatic tissue and self-maintenance, but individuals consuming MPs still had lower desiccation tolerance. Warming and MPs both promoted food consumption, but they differentially affected the life-history tradeoff between investment into self-maintenance vs. reproduction. In sum, appetite, life-history strategy, and dynamics in the digestive tract may be critical to animals simultaneously exposed to warming and MPs.