Transgenerational toxicity of tralomethrin in zebrafish: Parental exposure induces developmental defects in offspring.

Tralomethrin (TRA), a widely used type II pyrethroid insecticide, belongs to a class of pesticides frequently detected in aquatic environments, raising concerns about its potential chronic and transgenerational toxicity. This study aimed to evaluate the long-term effects of environmentally relevant concentrations of TRA (0.05, 0.5, and 5 μg/L) on adult zebrafish and their offspring. Adult zebrafish were exposed to TRA for 150 days, during which phenotypic observations, histological assessments, biochemical assays, transcriptomic profiling, and developmental evaluations of F1 progeny were conducted. Following TRA exposure, male zebrafish exhibited increased body weight, and a significant decline in spawning rate was observed. Histological and biochemical analyses revealed gill and ovarian abnormalities, accompanied by oxidative stress and apoptosis in ovarian tissues. Transcriptomic analysis of TRA-exposed ovaries revealed gene enrichment in glutathione metabolism and signaling pathways including Hedgehog and Wnt, reflecting oxidative stress and developmental disruption. In the F1 generation, TRA exposure led to decreased survival and hatching rates, along with developmental abnormalities including pericardial edema, spinal curvature, and impaired swim bladder inflation. Gene expression analyses of swim bladder marker genes and regulatory pathways further corroborated TRA-induced disruption in organogenesis. Overall, these findings demonstrate that chronic TRA exposure can induce multi-level toxic effects in zebrafish, including reproductive impairment and transgenerational developmental defects. This study highlights the urgent need to assess the ecological risks of pyrethroid pesticides and to incorporate long-term and transgenerational endpoints into environmental risk assessment.