Effects of Atrazine on Anuran Development are Altered by the Presence of a Nonlethal Predator

Abstract

Although predator-induced stress is a common biotic factor in aquatic communities that can strongly influence anuran development, there have been no studies to date that examined the interaction between this factor and atrazine, the most widely used pesticide in the United States. The potential synergistic effects of atrazine (0, 20, or 200 microg/L) and predatory stress on the survival, growth, development, and reproductive development of Hyla versicolor (gray treefrog) tadpoles were investigated. Atrazine reduced the proportion of tadpoles reaching metamorphosis; however, this effect was modified by the presence of a nonlethal predator. The combined effects of predatory stress and exposure to 200 microg/L atrazine resulted in the lowest proportion of tadpoles reaching metamorphosis. No treatment effects were observed for mass, snout-urostyle length, or the proportion of metamorphs that were male or female. No macroscopic gonadal anomalies were observed. Many gonads were underdeveloped; however, gonadal development was more advanced in metamorphs exposed to 200 microg/L atrazine. This effect was modified by the presence of a nonlethal predator such that female gonadal development was further accelerated and male gonadal development was retarded by predatory stress. These results indicate that simplified laboratory studies may not accurately reflect the effects of atrazine on anuran development in natural communities.

Interactions of environmental stressors impact survival and development of parasitized larval amphibians

“…This is inconsistent with results reported by Lafiandra et al (2008), but a lower atrazine concentration was used in the present study. Predation cues alone had no significant effect, but individuals exposed to predation cues were more developed than those not exposed to predator cues in 3 lg/L atrazine, while the opposite pattern was observed in the absence of atrazine.…”

“…Atrazine has also been shown to increase larval amphibian susceptibility to trematode infection (Kiesecker 2002), but it is not known how infected hosts respond to atrazine exposure in comparison to uninfected individuals. However, it is possible that interactive effects could occur, given that the presence of an additional stressor (predators) causes sublethal concentrations of atrazine and other pesticides to become lethal to larval frogs (e.g., Relyea and Mills 2001, Relyea 2004, LaFiandra et al 2008.…”

Cryptic confounding compounds: a brief consideration of the influences of anthropogenic contaminants on courtship and mating behavior

“…While the direct effect may be obvious, cascading effects on higher trophic levels can be overlooked (Clotfelter et al 2004; Clements and Rohr 2009; Tuomainen and Candolin 2011). These effects can be overshadowed by the complexity of ecosystems and by synergistic interactions between multiple contaminants and between contaminants and natural stressors (e.g., Kuiken et al 1994; Boone and Semlitsch 2003; LaFiandra et al 2008; Brooks et al 2009; Pestana et al 2009). Adding animal behavior as a factor to understanding ecosystem interactions significantly complicates the challenge of managing conservation efforts, but it is one for which we must account if we are to fully appreciate the scope of the detrimental effects of anthropogenic stressors.…”

Gonadal abnormalities in frogs (Lithobates spp.) collected from managed wetlands in an agricultural region of Nebraska, USA

“…Neither have the endocrine-mediated effects of atrazine been consistently observed for the most studied species, Xenopus, or among frog species generally (Carr et al, 2003;Coady et al, 2004Coady et al, , 2005Du Preez et al, 2009;Jooste et al, 2005;Kloas et al, 2009;LaFiandra et al, 2008;Oka et al, 2008;Storrs-Ménedz and Semlitsch, 2009). Similarly, field studies have not consistently associated high environmental levels of atrazine with biased sex ratios or testicular oocytes (Murphy et al, 2006;Spolyarich et al, 2010).…”