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Behavioural impact of microplastics on zebrafish development
Summary
Scientists exposed baby zebrafish to jagged, real-world-like microplastic fragments (like those actually found in household dust and water, rather than the perfectly round plastic beads typically used in lab studies) and found the fish developed damaged sensory organs, causing them to react much slower to touch. This suggests that the irregular shape of microplastic pollution, not just its size, may cause hidden nerve and sensory damage, raising concerns about what similar exposure could mean for sensory or nervous system health in other animals, including potentially humans.
Microplastic (MP) pollution in aquatic environments is ubiquitous and characterized by particles of highly irregular shapes. Yet, most laboratory studies examining MPs impacts on aquatic species rely on pristine polymer spheres, which poorly reflect the diversity and complexity of environmental MPs. In this study, we assessed the developmental effects of household-derived, irregular MP fragments, on zebrafish. Fragments of synthetised MPs used in this study displayed heterogeneous sizes and jagged shapes. Acute exposure to all MP types did not induce embryonic lethality or gross malformations but did result in significant sublethal toxicity: exposed larvae showed reduced touch-evoked escape responses, consistent with a pronounced loss or damage of lateral line neuromasts. To further characterize the underlying sensory impairment, we examined neuromast structure and function, which revealed mechanical disruption, kinocilia fusion, and reduced mitochondrial activity. Our findings emphasize that physical and physicochemical interactions associated with fragment morphology and polymer availability drive neurosensory toxicity more than particle size alone. This work highlights that acute MP exposure disrupts key sensory behaviours and structures critical for ecological fitness. Overall, these results support the need for increased regulatory and scientific attention to behavioural and sensory endpoints in MP risk assessments.