A life stage study of Hyla cinerea exposed to atrazine: Quantifying body burdens and metabolites
Authors:Amanda Ballard, Donna Glinski, Robin Van Meter
Mentor:Tom Purucker, Ecologist , US Environmental Protection Agency Ecosystems Research Division
In the Southeastern United States, pesticide exposures pose a risk to amphibians via dermal uptake. Agricultural developments have overlapped with amphibian territories, causing exposure risks. This may be a contributing factor in the widespread global decline of amphibian populations. Prior studies have quantified the dermal uptake of pesticides in amphibians; however, research on the effect of repeated exposures among the different life stages is limited. This study was designed to measure pesticide body burdens after two life stage exposures to determine how multiple exposures affect the ability of frogs to take up and metabolize pesticides. During summer 2013, the exposure of atrazine on green treefrogs (Hyla cinerea) was tested. Atrazine is one of the leading pesticide active ingredients in the United States. Green treefrogs were reared from embryos through two weeks post-metamorphosis at the United States Environmental Protection Agency’s (US EPA) Research Division in Athens, GA. At Gosner stage 28, a subset of tadpoles was exposed to 20 ppb atrazine, an environmentally relevant value, for 24 hours. At two weeks post metamorphosis, all frogs were exposed to atrazine, in an aquatic or terrestrial environment. Atrazine and its metabolites, desethyl-atrazine (DEA) and deisopropyl atrazine (DIA), were extracted and concentrations were quantified using Liquid Chromatography-Mass Spectroscopy. All exposed individuals showed measurable atrazine, DEA and DIA body burdens. In the aquatic exposure, body burdens were consistently greater in the frogs not exposed as tadpoles. This suggests that environmentally relevant concentrations of atrazine may induce increased tolerance, showing an adaptation to anthropogenic influence. However, in the terrestrial exposure, the atrazine body burden was significantly greater in the pre-exposed frogs. This suggests that the moisture level of the environment in which they are exposed may reverse this tolerance. Future direction of this study is to delve into the physiological pathways associated with this induced resistance.