The effect of carbaryl and glyphosate pesticides on killifish (Fundulus heteroclitus) feeding behavior

Abstract

Pesticide runoff into tidal creeks is a concern due to its neurotoxicity to fish. One effect pesticides can have on tidal creek fish is disabling their ability to find and consume food. The current study examined the effect of two commonly used pesticides, carbaryl (Sevin) and glyphosate (Round – up), on feeding in Fundulus heteroclitus (killifish). Killifish are an important member of the salt marsh food web and are tolerant to wide environmental fluctuations. Killifish caught in Georgia tidal creeks were brought to the lab for feeding experiments. Thirty fish were exposed to each pesticide either at the LC50s (a concentration lethal to 50% of the fish tested during a 96 hour period) or half of the LC50 concentration for 24 hours, without food, prior to testing. Fish were tested individually by placing them in a t-maze and recording the time it took them to find and consume shrimp pellets. Approximately 200 mg of shrimp pellets [ND1] were placed in one arm of the t-maze and alternated between the arms for each test. The fish had 10 minutes to find and consume the food. Fish exposed to glyphosate or carbaryl were either unable to consume pellets or took significantly (3 – 4 times) longer to find and consume shrimp pellets as compared to control fish (p < 0.0001 for both pesticides). This occurred in fish exposed to both LC50 and half LC50 concentrations, although the effect was more pronounced at the higher concentrations. Based on these results, both carbaryl and glyphosate can adversely affect the killifish’s ability to feed, which can have consequences throughout the salt marsh food web.