NPs muscle toxicity
Nanoplastics pose growing threat to aquatic environments, but their sublethal impacts on ecologically critical behaviors like swimming, which directly determines migration success, and the underlying muscular mechanisms are still not well characterized. This study investigated the impact of NPs on skeletal muscle and swimming performance in the migratory large yellow croaker (Larimichthys crocea). Through a multi-concentration exposure experiment, and by integrating behavioral assays, ultrastructural histopathology, transcriptomics, and metabolomics, the results showed that 30 d of NPs exposure significantly inhibited growth and impaired both sustained (Ucrit) and burst (Ucat) swimming capacities in a concentration-dependent manner. Ultrastructural analysis revealed progressive muscle damage, from fiber disorganization to sarcomere disintegration. Integrated transcriptomic and metabolomic profiling identified a potentially conserved toxic effect pattern across fish species involving cellular barrier breakdown, a metabolic decoupling energy crisis, and specific perturbation of tryptophan metabolism which may amplify inflammatory responses. We also systematically revealed the progressive mechanisms of NPs induced muscle toxicity, as initial endocrine and metabolic disruption at low concentrations, shifting to oxidative stress and energy reallocation at moderate levels, and culminating in ferroptosis and excessive autophagy at high exposure. Our findings establish a direct link from NPs induced molecular and structural muscle damage to locomotor deficiency. This work demonstrates that sublethal NPs exposure can critically undermine swimming capabilities, thereby threatening migration and other vital life-history traits in fish. The results underscore the need to incorporate behavioral endpoints into environmental risk assessments of plastic pollution to safeguard aquatic ecosystem health.