Effects of predator cues on pesticide toxicity: Toward an understanding of the mechanism of the interaction

Abstract

Pesticide toxicity may be modified by a number of co-occurring environmental and ecological stressors. Coexposure to predator cues has been shown to potentiate and/or synergize toxicity of pesticides. However, the mechanisms behind these interactions are not well understood. Here we examine the effects of fish predator (bluegill, Lepomis macrochirus) cues on toxicity of five different pesticides to the freshwater cladoceran, Ceriodaphnia dubia. The purpose for examining patterns among pesticides was to test the idea that the mechanism of the interaction could be explained by a general stress response; that is, the interaction patterns would be similar regardless of the pesticide's mechanism of action [MOA]). Acute 96-h concentration-response experiments were conducted for pesticides with and without fish cues. Predator cues influenced the toxicity of pesticides and the interaction patterns varied among pesticides. Fipronil exhibited a synergistic interaction, while predator cues interacted antagonistically for bifenthrin and thiacloprid. Other compounds previously reported to potentiate toxicity (malathion) were found to act additively. The results demonstrate that factors such as pesticide bioavailability, K(OC) , and exposure concentration may be important for predicting the occurrence of these interactions and that patterns were not consistent among pesticides varying in MOA. Predator stress is an important component for structuring communities and ecosystem processes. Fully understanding how this process may interact with organic contaminants may best be achieved by examination at toxicokinetic and toxicodynamic scales.

Impact of Predator Cues on Responses to Silver Nanoparticles in Daphnia carinata

“…In brief, two healthy adult bluegills (total body length approximately 18 cm) were randomly selected from the culture tank and placed in a glass tank with 20 L of synthetic MH water for 2 h. The culture water was then filtered through a 1-lm glass fiber filter to remove particles and then was used as the fish-conditioned water in Daphnia experiments. Previous studies have shown that this method of water conditioning resulted in a relatively constant chemical cues solution that led to reproducible biological responses in daphnids (Rose et al 2001;Qin et al 2011). MH water and fish-conditioned water were prepared freshly before each experiment.…”

“…Dissolved organic carbon (DOC) concentrations in MH water and fish-conditioned water were analyzed with a total organic carbon (TOC) analyzer (model 1020; O.I. Analytical, College Station, Texas, USA [Qin et al 2011] ).…”

“…Preparation of predator-conditioned water was performed as described previously (Qin et al 2011). In brief, two healthy adult bluegills (total body length approximately 18 cm) were randomly selected from the culture tank and placed in a glass tank with 20 L of synthetic MH water for 2 h. The culture water was then filtered through a 1-lm glass fiber filter to remove particles and then was used as the fish-conditioned water in Daphnia experiments.…”

“…It is known that predator cues can have profound effects on the behavior, abundance, and population structure of aquatic prey organisms (Chivers and Smith 1998). Moreover, recent studies found that predator cues can interact with a variety of chemicals such as metals (Barry 2011) and pesticides (Qin et al 2011;Giri et al 2012;Janssens and Stoks 2013b), thus altering their toxic effects on aquatic prey organisms. These findings raise concern that predator cues could play an important role in the process of how contaminants exert their effects on aquatic prey organisms.…”

An Investigation of the Effect of Malathion on Adaptive Plasticity of Pseudacris Sierra

“…How pesticides interact with predation rates is largely unknown, but the few studies conducted have shown that agrochemicals have both positive and negative impacts through indirect and direct effects on predation (Relyea et al, 2010;Qin et al, 2011). Sub-lethal concentrations of pesticides can impair tadpoles' ability to recognize and behaviorally respond to predators (Bridges et al, 1999).…”