Screening anti-predator behaviour in fish larvae exposed to environmental pollutants

Predation is one of the main sources of mortality for fish larvae. During evolution, they have developed different anti-predator behaviours, as the vibrational-evoked startle response and its habituation, for promoting survival to predator's strikes. Whereas these two behaviours can be altered by the exposure to some neurotoxicants, it is currently unknown if the exposure to environmentally relevant concentration (ERC) of neurotoxic pollutants could impair them. In this study thirty neurotoxic environmental pollutants from nine chemical groups, including: herbicides; carbamate, organophosphate (OP), organochlorine (OC), neonicotinoid and pyrethroid insecticides; toxins; metal and non-metal elements, have been screened at two concentrations, including one environmental relevant concentration (ERC), for adverse effects on anti-predator behaviours by using the Vibrational Startle Response Assay on zebrafish larvae. Significant effects over anti-predator responses were equally observed in both exposure concentrations. Focusing on the ERC scenario, it was found that the startle response was the less affected behaviour, where ten pollutants from all chemical groups except for organochlorine, neonicotinoid and pyrethroids, altered this response. Interestingly, organic and inorganic pollutants showed opposite effects on this response: whereas all organic pollutants decreased the startle response, the three remaining inorganic pollutants increased it. On the other hand, more pollutants affected habituation of the startle response of the larvae, where thirteen of the pollutants from all groups, except for herbicides, altered this behaviour at ERC, generally resulting in a faster habituation except for one OP and one marine toxin, which were able to delay this response. Ultimately, only one chemical from the OP, toxin, metal and non-metal element groups altered both the startle response and its habituation at both ERC and WSC. These results emphasize the environmental risk of the current levels of some neurotoxicants present in our aquatic ecosystems, as they are high enough to impair essential anti-predator behaviours in fish larvae.