Biological Impacts of Microplastic Exposure in Zebrafish (Danio rerio): A Systematic Review Across Developmental, Physiological, and Neurobehavioral Endpoints

Abstract

Microplastics (MPs) are emerging pollutants widespread in aquatic environments; however, their effects across the different life stages of aquatic organisms remain poorly understood. This systematic review integrates recent experimental results on the developmental, physiological, and neurobehavioral effects of MP exposure on zebrafish (Danio rerio), a popular model organism for ecotoxicology research. A PRISMA-guided search using Web of Science (WoS) and Scopus as databases generated 581 articles, which were screened to 60 eligible articles. The collated results showed that MP toxicity at various life stages of zebrafish was strongly related to the physicochemical properties of MPs and exposure conditions. In terms of developmental toxicity, peer-reviewed publications assessing specific MP physicochemical properties—polymer type, size, concentration, shape, and degree of aging—reported concentration-dependent effects, with increasing MP concentrations generally associated with growth inhibition, cardiac dysfunction, increased malformations, and lower hatching rate, particularly at ≥10 mg/L to ≥100 mg/L. However, several studies noted that under particle-based exposure scenarios, MP toxicity exhibited threshold-like or non-monotonic responses, attributed to aggregation, bioavailability, and uptake dynamics. Weathered and artificially aged MPs exhibited higher embryotoxicity and neurodevelopmental toxicity, including changes in gene expression of neurons, decreased integrity of motor neurons, and impaired retinal development, compared with “virgin” MPs. In terms of physiological endpoints, oxidative imbalance like changes in the activity of antioxidant enzymes (superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx)), lipid peroxidation, inflammation, and disruption of tight junctions have been reported as key toxicity pathways. Chronic MP exposure in zebrafish also caused changes in the gut microbiota, hepatic metabolism, endocrine disruption, reproductive damage, thyroid function disruption, and genotoxicity in zebrafish. In terms of neurobehavioral effects, changes in locomotor activity, anxiety response, neurotransmitter homeostasis, and acetylcholinesterase function, have been observed, in both larvae and adults, with a potentiation effect in aged MP exposure. Finally, this systematic review found major limitations for inter-study comparisons because of inconsistencies and differences in methodology applied related to MP concentration, simulation of natural MP aging, and MP dose measurements.