Evidence of microplastic transfer from larvae to adult Amphipsyche meridiana (Hydropsychidae, Trichoptera) in an irrigation canal

Plastic pollution has become an important environmental issue, with massive amounts of plastic waste accumulating in both aquatic and terrestrial areas. Due to the abundance of microplastics (MPs) in aquatic environments, aquatic organisms will unavoidably ingest them and pass them up the food chain. This study investigated how microplastics are transferred across distinct life stages of the aquatic insect Amphipsyche meridiana, specifically between its aquatic and flying stages, which require different environmental conditions. For the first time, this work demonstrates that MPs can be transferred ontogenically from a feeding life stage (larva) of ~0.1 MP items per individual to a non-feeding life stage (pupa) of ~0.64 MP items per individual and lastly to the adult terrestrial life stage (~0.13 MP items per individual). MPs ranging in size from less than 100 µm to larger than 500 µm can readily be transferred into pupae and adult stages. The move of MPs to adults suggests a potential aerial avenue for contamination of the new habitat. Therefore, any organism that feeds on freshwater insects during their terrestrial life stage could be impacted by MPs found in aquatic habitats. Our findings revealed that in insects with metamorphosis, MPs can move from feeding larvae to nonfeeding pupae in aquatic habitats and then to adults flying to land. Caddisflies can participate in MP circulation in the environment. It was critical to note that the investigated aquatic insects shared similar MPs (size, shape, and color) with those observed in river water. It demonstrates the potential for insects (MP accumulators) to act as a driving force in MP transfer across different habitats. It has also been discovered that an aquatic insect's feeding habitat and host reservoir may be responsible for MP ingestion.