Ecotoxicity assessment of triphenyl phosphate (TPhP) exposure in Hoplobatrachus rugulosus tadpoles

Triphenyl phosphate (TPhP), a widely used aromatic organophosphate flame retardant, is known to accumulate in organisms through water, air, and soil, consequently, causing toxicity. This study is the first to evaluate the acute and sub-chronic toxicities of TPhP to amphibians. In the acute toxicity analysis, the 96-h median lethal concentration (LC50) for GS35 Hoplobatrachus rugulosus tadpoles was 2.893 mg/L, and the 10% effect concentration (EC10) was 289 μg/L. After two weeks of exposure to low TPhP concentrations, the survival and metamorphosis rates of H. rugulosus tadpoles decreased, and the metamorphosis time was prolonged as the TPhP concentration increased. The threshold concentration that affected tadpole survival and metamorphosis time was 50 μg/L and 100 μg/L, respectively. No significant differences were observed in the condition factor and hepatic somatic index of the tadpole after metamorphosis; however, tadpole body mass and TPhP concentration were negatively correlated. Further, TPhP inhibited the expressions of Cu-Zn sod and cat, thereby reducing the activities of superoxide dismutase and catalase in the tadpole liver. The threshold for affecting gene expression and enzymatic activity was 100 μg/L. These findings provide significant insights on the stress ecology of aquatic organisms.