The Development of Yellow Mealworm ( Tenebrio molitor ) as a Cheap and Simple Model to Evaluate Acute Toxicity, Locomotor Activity Changes, and Metabolite Profile Alterations Induced by Nanoplastics of Different Sizes

Due to the wide uses of plastic products, nanoplastics are ubiquitous contaminants in the environment. Hence, extensive studies used various models to evaluate the toxicity of nanoplastics. In the present study, we developed yellow mealworm (Tenebrio molitor) as an alternative model to investigate the acute toxicity of nanoplastics. Our results showed that microinjection with 500 mg/kg nanoplastics significantly increased death rate of yellow mealworms after 24 or 48 h, with 100 nm particles being more effective compared with 20 nm ones. Meanwhile, dose-dependent increase of death rate was observed in yellow mealworms after injection with 2-200 mg/kg 100 nm nanoplastics. Exposure to 2 mg/kg 100 nm but not 20 nm nanoplastics also led to hyperactivity of yellow mealworms. Both types of nanoplastics altered metabolite profiles, that 20 nm nanoplastics significantly up-regulated and down-regulated 9 and 12 metabolites, whereas 100 nm nanoplastics significantly up-regulated and down-regulated 16 and 25 metabolites, respectively. Enrichment analysis revealed that 100 nm but not 20 nm nanoplastics significantly affected alpha-linolenic acid metabolism (ko00592) and purine metabolism (ko00230). For the metabolites belonging to these pathways, 100 nm nanoplastics significantly up-regulated stearidonic acid but down-regulated guanine. Combined, these results revealed size-dependent effects of nanoplastics on acute toxicity, hyperactivity and metabolite profile changes in yellow mealworms. These results also indicated the potential uses of yellow mealworms as a cheap and simple model to evaluate the toxicity of nanoplastics.