What can crickets teach us about the thermal biology of microplastics?

Microplastics (MPs) are small-sized (< 5 mm) bits of plastic that have been found in every type of ecosystem and in many types of human tissue. Accumulation of MPs can lead to toxicity for many organisms. In addition to MPs, animals’ environments regularly experience temperature shifts, and the biology of over 99% of animals is tightly linked to environmental temperatures that are rapidly warming due to climate change. Thus, temperature shifts (e.g., global warming) and MP exposure are two features of environmental change that may have synergistic effects on animals. For example, warmer temperatures may increase the consumption of MP-contaminated food sources and, thus, increase the costs of MP exposure (e.g., reduced reproductive investment). The costs of ingested MPs are likely highest when MPs get absorbed through the lining of the digestive tract and interact with (and potentially damage) internal body tissues. Here, we fed nylon MPs to a local field cricket (Gryllus lineaticeps) to explore the effects temperature (23℃, 28℃, or 33℃) on: (1) the number of MP filaments absorbed through the digestive lining and into the body cavity, and (2) investment into reproductive and somatic tissues. We compared these results to G. lineaticeps that were not exposed to MPs. Our study will determine the independent and interactive effects of temperature and MPs on fitness-related traits, and it will provide new insight into the thermal biology of MPs in insects.