Sublethal effects of acetaminophen exposure on benthic aquatic animal (Hydra magnipapillata)

Background: Acetaminophen (APAP) is widely used to alleviate pain and fever in human. It is one of the drugs most commonly detected in the environment, and a potential threat to aquatic organisms. This study provides valuable insight into the possible toxic effects of APAP in aquatic organisms. Objective: The adverse effects of APAP were investigated in a benthic animal, Hydra magnipapillata. Results: We found that although APAP did not induce lethal effect on the animal, it did inhibit regeneration of the tentacles at the minimum concentration of 150 mg/L, while it showed no effect on the regeneration of the hypostome. The median inhibitory concentrations (IC₅₀) for tentacles regeneration in H. magnipapillata for (72 and 96) h were (231.3 and 487.9) mg/L, respectively. Gene expression level changes in the exposed H. magnipapillata showed that the genes were mostly upregulated, and APAP could induce oxidative stress, DNA damage, protein damage, genomic instability, gametogenesis disorder, and abnormal morphogenesis. Conclusion: Toxicity level of APAP in H. magnipapillata is relatively low, and showed non-lethal effects. However, at relatively high concentration, APAP could inhibit the regeneration of tentacles that may affect its life abilities. At relatively low concentration, APAP exposure induces various physiological effects that may affects its reproductive activity and morphological development.