The herbicide atrazine induces hyperactivity and compromises tadpole detection of predator chemical cues

Abstract

The ability to detect chemical cues is often critical for freshwater organisms to avoid predation and find food and mates. In particular, reduced activity and avoidance of chemical cues signaling predation risk are generally adaptive behaviors that reduce prey encounter rates with predators. The present study examined the effects of the common herbicide atrazine on the ability of Cuban tree frog (Osteopilus septentrionalis) tadpoles to detect and respond to chemical cues from larval dragonfly (Libellulidae sp.) predators. Tadpoles exposed to an estimated environmental concentration of atrazine (calculated using US Environmental Protection Agency software; measured concentration, 178 μg/L) were significantly hyperactive relative to those exposed to solvent control. In addition, control tadpoles significantly avoided predator chemical cues, but tadpoles exposed to atrazine did not. These results are consistent with previous studies that have demonstrated that ecologically relevant concentrations of atrazine can induce hyperactivity and impair the olfactory abilities of other freshwater vertebrates. The authors call for additional studies examining the role of chemical contaminants in disrupting chemical communication and the quantification of subsequent impacts on the fitness and population dynamics of wildlife. Environ Toxicol Chem 2016;35:2239-2244. © 2016 SETAC.

Stormwater wetlands can function as ecological traps for urban frogs

“…The attraction towards predator olfactory cues by tadpoles raised in the most contaminated conditions mirrors similar responses observed in Cuban tree frog tadpoles after exposure to the pesticide atrazine (Ehrsam et al. ). Interestingly, when both visual and olfactory cues were presented in concert, tadpoles raised in LQ treatments avoided predators (unlike when purely visual cues were provided when no response was observed).…”

“…For example, Cuban tree frog tadpoles do not avoid predator cues and are hyperactive following exposure to the herbicide atrazine (Ehrsam et al. ). These types of behavioral changes can indirectly reduce fitness by increasing the probability of predation (Broomhall ).…”

“…Contaminants common in stormwater wetlands can also cause maladaptive behaviors to develop via olfactory disruption (Tierney et al 2010). For example, Cuban tree frog tadpoles do not avoid predator cues and are hyperactive following exposure to the herbicide atrazine (Ehrsam et al 2016). These types of behavioral changes can indirectly reduce fitness by increasing the probability of predation (Broomhall 2004).…”

Atrazine and amphibians: Data re-analysis and a summary of the controversy

“…endocrine disruptors)(Lurling and Scheffer 2007, Rohr et al 2009). Several studies have shown that atrazine can reduce chemical detection of cues from predators and mates (Moore and Waring 1998, Tierney et al 2007, Ehrsam et al 2016) and others have shown that it can affect cell-to-cell communication by altering hormones, such as stress hormones (Gabor et al 2016, McMahon et al 2017), thyroid hormones (Larson et al 1998), and sex hormones (Hayes et al 2003, Hayes 2003). Given that much of the controversy regarding atrazine and amphibians involves its effects on amphibian sex hormones and gonadal development, this topic will be discussed in more detail in the “A Timeline of the Atrazine-Amphibian Controversy” section.…”

“…One of the biggest concerns regarding the effects of atrazine on amphibians is that atrazine regularly interacts with other stressors commonly experienced by amphibians, either additively or synergistically. For example, particular climatic conditions, such as increased drying (Rohr et al 2004, Rohr and Palmer 2005, 2013) and particular biotic conditions, such as parasitism (Rohr and McCoy 2010b) and predation risk (Rohr and Crumrine 2005, Ehrsam et al 2016) can be worsened by atrazine. Atrazine also additively or synergistically interacts with other common agrochemicals (Rohr et al 2008c, Halstead et al 2014).…”