Field-Recovered Polystyrene Exposure Alters Developmental Endocrine Signaling and Cholinergic Function in the Plastivorous Insect Zophobas morio

The use of insect larvae for plastic waste biodegradation has attracted increasing attention as a potential strategy to mitigate environmental plastic pollution. However, the toxicological consequences of ingesting plastics recovered from the environment, particularly those acting as vectors for sorbed contaminants, remain poorly understood. In this study, we investigated the endocrine and neurotoxic effects of field-recovered (environmental) polystyrene (ePS) in the plastivorous insect Zophobas morio. Larvae were fed virgin PS (vPS) or PS collected from a marine coastal area known to be impacted by anthropogenic activities. Chemical analyses revealed that ePS was characterized by a mixture of organochlorine and organophosphorus pesticides, with a total complex residue concentration of 23.7 ± 5.5 µg g−1, whereas only trace levels of hexachlorocyclopentadiene (HCCPD) were detected in vPS (2.55 ± 0.65 µg g−1). All compounds detected in ePS were also detected in larvae from the ePS-fed group, indicating effective trophic transfer from plastic to the organism. Despite the absence of mortality, PS-fed larvae exhibited reduced growth compared to controls. At the molecular level, ingestion of ePS caused a significant downregulation of key genes involved in the ecdysteroid signaling pathway (ecdysone receptor, EcR; ultraspiracle, USP; and early response genes E74 and E75), coupled with an upregulation of juvenile hormone-responsive genes (methoprene-tolerant, Met; Krüppel homolog 1, Kr-h1), suggesting endocrine imbalance potentially affecting developmental progression. In parallel, acetylcholinesterase (AChE) enzymatic activity was significantly inhibited, particularly in larvae fed ePS, despite no changes in AChE or acetylcholine receptor transcript levels, indicating functional neurotoxicity. This study highlights the importance of considering plastic-associated contaminant toxicity when evaluating insect-based plastic biodegradation strategies.