The effects of triclosan on reflex responses and anti-predator behavior in an estuarine fish

Background/Question/Methods

Triclosan is a common antibacterial compound found in an increasing number of personal care products including toothpastes, deodorants, and soaps. Despite partial removal by wastewater treatment plants, an increasing amount of triclosan is entering watersheds where it can have significant effects on aquatic organisms. Even at low levels, triclosan negatively impacts thyroid homeostasis in anurans and fish, and it can decrease startle responses and activity levels in anurans. The purpose of this research was to investigate the effects of triclosan on reflex responses and anti-predator behavior in juvenile Atlantic croaker (Micropogonias undulatus), an estuarine fish. Sixty Atlantic croaker were held in individual tanks and randomly assigned to be fed a diet of either normal food pellets or pellets impregnated with 50 ppm triclosan for 14 days. Both prior to and immediately following the 14 day exposure, fish were tested for a suite of reflex action mortality predictors (RAMP) and were subjected to a video-recorded 30 second simulated predator attack. Videos were then analyzed for the specific strategies (run, hide, cut across tank, turn gambit) employed by the fish before and after exposure.

Results/Conclusions

We found that fish exposed to triclosan were significantly more likely than control fish to exhibit reflex impairment. Specifically fish lost the dorsal spine erection response, meaning that they did not raise their dorsal fin when the fin was flattened. Reflex impairment is correlated with increases in overall fish stress and mortality outcomes. Treated fish also experienced significant shifts in their anti-predator strategies. Triclosan-exposed fish spent significantly more time in their post-exposure test hiding from the simulated predator than fish in the control group. In some cases, fish continued to stay stationary even as the simulated predator touched them. The results of this study indicate that triclosan does impair fish reflexes and creates shifts in the strategies used by croaker to escape their predators. Since these schooling fish have been shown to exhibit dominance hierarchies, triclosan may affect social patterning in Atlantic croaker. These behavioral effects may have important implications not only for croaker and similar fish species but also for croaker predators such as bottlenose dolphins as contaminated fish may be easier prey, leading to increased predator body burdens.