Behavioral effects of carbaryl and temperature on killifish Fundulus heteroclitus

Abstract

Killifish, Fundulus heteroclitus, are stress tolerant fish found in salt-marshes along the Georgia coast. They can withstand tidal fluctuations in salinity and temperature and are important members of the salt-marsh food web, making them a valuable test subject for pollutant effects. We observed the effects of carbaryl exposure, in conjunction with temperature variations, on killifish behavior. Carbaryl is a commonly used pesticide (Sevin™) and has neurotoxic effects at sub-lethal levels on fish. Killifish were exposed to varying carbaryl concentrations for 24 hours: 28.75 µg/L (LC50 for carbaryl in killifish), 13.8 µg/L, 6.9 µg/L, and 3.4 µg/L at temperatures of 22ºC and 26ºC, normally found in Georgia tidal creeks. Prior to and after exposure, fish were placed in a T-maze and given 10 minutes to consume food placed in a distant arm of the T. Time to find food and swimming behavior were recorded for each fish (n=15 per treatment). Tissue samples were then taken from each fish to quantify carbaryl concentration via ELISA. In general, fish exposed to carbaryl took longer to find food compared to controls, and had a concomitant increase in tissue carbaryl concentration. Paradoxically, fish held at the lower temperature had higher body carbaryl loads, while fish held at the higher temperature exhibited more abnormal behavior and decreased feeding success. These results show an adverse effect of carbaryl on killifish behavior, exacerbated by exposure to elevated water temperature. A decline in killifish feeding ability may have impacts throughout the food chain, given their important ecological niche.