Plastic bag and facial cleanser derived microplastic do not affect feeding behaviour and energy reserves of terrestrial isopods
Current data regarding the effects of microplastic (MP) on terrestrial organisms are very scarce. Isopods play an important role in plant litter decomposition processes and are commonly used test species in terrestrial ecotoxicity studies. Their altered feeding behaviour and energy reserves are established biomarkers of adverse effects upon stressor exposure. For this study we assessed the effects of MP derived from plastic bag film (mean size 183 ± 93 μm) and particles from a facial cleanser (mean size 137 ± 51 μm) on the terrestrial isopod, Porcellio scaber. Isopods were exposed to MP via feeding on food pellets (4 mg g−1 dry weight; 0.4% w w−1) for 14 days under laboratory conditions. A control group was exposed to food pellets with no MP added. In line with previously suggested modes of MP action on animal ingestion, we assessed the food ingestion rate, defecation rate, food assimilation rate and efficiency, body mass change, mortality and energy reserves (proteins, carbohydrates, and triglycerides) in the digestive glands (hepatopancreas) of individual isopods. Contrary to our expectations, no effects on either end-point were observed under the given exposure conditions. Further work should be carried out to investigate the potential longer-term effects of such exposure. We conclude that 14 days exposure to plastic bag and facial cleanser MP is not severely hazardous to isopods.