Adverse effects of thimerosal on the early life stages of zebrafish

Thimerosal (THI) is an organic mercury compound that is widely used in drugs, vaccines and antibacterial products. Its extensive production and use have resulted in significant environmental contamination, posing a considerable threat to aquatic life. However, the knowledge of the toxicity of THI to aquatic organisms is still insufficient. In this study, we conducted a 5-day THI exposure experiment using zebrafish, from 0 to 5 days post fertilization (dpf). The possible adverse effects of THI on the early-life stages of zebrafish were explored by investigating variations in their physiological parameters, behavioral traits, and neurotransmitter levels. The results showed THI exhibited significant developmental toxicity to aquatic organisms. Exposure to THI significantly induced serious malformation (at 50 μg/L), accelerated hatching, and elevated heart rate (at 5 and 50 μg/L). The behavioral traits of zebrafish larvae had an increased first and then decreased relationship with increasing concentration of THI, which induced hyperactivity at 0.5 μg/L but opposite at 50 μg/L. Furthermore, exposure to 50 μg/L THI significantly raised levels of 5-HT, 5-HIAA, DA, DOPAC and ACH in zebrafish larvae. In addition, several significant correlations between behavioral traits and the neurotransmitter contents were detected, which seemed to reveal an important mechanism of the neurobehavioral toxicity of THI to fish.