Microplastics affected black soldier fly (Hermetia illucens) pupation and short chain fatty acids

Microplastics (MPs) are microscopic particles that are now found in almost all ecosystems where they may exert adverse effects on various organisms, including insects. In this study, 20 black soldier fly (Hermetia illucens) larvae (BSFL) were exposed to MPs, in the form of polypropylene (PP-MPs; 55 ± 4 µm) at 0.22% (26,972,507 particles/kg), versus a control (no added MPs) in triplicate for two weeks. After two weeks, final lengths, weights, percentage of pupation, fatty acid composition of BSFL and substrate reduction percentage were measured. Survival, lengths/weights and percentage substrate reduction in the PP-MP group were not significantly different from the control. However, percentage of pupation was significantly lower in the PP-MP treatment (at 65.2%) compared to the control (at 83.8%). Among the measured fatty acids, only propionic and butyric acid changed, and these short-chain fatty acids (SCFAs) significantly increased from 0.12% and 0.17% to 0.14 and 0.19%, respectively, in the PP-MP-exposed group. This study indicates that exposure to environmentally relevant levels of PP-MPs can substantially delay development, while the increase in the SCFA may indicate a change in the gut microbiota.