Hermaphroditic, demasculinized frogs after exposure to the herbicide atrazine at low ecologically relevant doses

Abstract

Atrazine is the most commonly used herbicide in the U.S. and probably the world. It can be present at several parts per million in agricultural runoff and can reach 40 parts per billion (ppb) in precipitation. We examined the effects of atrazine on sexual development in African clawed frogs (Xenopus laevis). Larvae were exposed to atrazine (0.01-200 ppb) by immersion throughout larval development, and we examined gonadal histology and laryngeal size at metamorphosis. Atrazine (>0.1 ppb) induced hermaphroditism and demasculinized the larynges of exposed males (>1.0 ppb). In addition, we examined plasma testosterone levels in sexually mature males. Male X. laevis suffered a 10-fold decrease in testosterone levels when exposed to 25 ppb atrazine. We hypothesize that atrazine induces aromatase and promotes the conversion of testosterone to estrogen. This disruption in steroidogenesis likely explains the demasculinization of the male larynx and the production of hermaphrodites. The effective levels reported in the current study are realistic exposures that suggest that other amphibian species exposed to atrazine in the wild could be at risk of impaired sexual development. This widespread compound and other environmental endocrine disruptors may be a factor in global amphibian declines.

Hypospadias: Interactions between environment and genetics

“…Hypospadias, whether associated with micropenis or not, has been reported in numerous wildlife species when the habitat is contaminated by pesticides [49]. The effects of prenatal xenoestrogens on animal male reproductive tract development have been studied by several groups.…”

Atrazine induction of a family 4 cytochrome P450 gene in Chironomus tentans (Diptera: Chironomidae)

“…Studies of its occurrence and behavior in streams and rivers draining agricultural lands have shown that the highest atrazine concentrations usually occur in relatively brief pulses following rain events, especially those that occur soon after herbicide application (DeNoyelles et al, 1982). However, significant effects of atrazine at ecologically relevant concentrations have been reported to cause hermaphroditism and demasculinization in male frogs exposed to 0.1 and 1.0 μg/l of atrazine (Hayes et al, 2002).…”

Water Contaminated With the Herbicide Atrazine: Alteration of Cancer Associated Tumor Protein D52-like 1 (tpd52l1) Gene Using the Zebrafish Model

“…Due to these controversial effects of atrazine, the EPA has set a limit, the Maximum Contaminant Level (MCL), to 3 parts per billion (ppb; µg/L) in drinking water; however, traces higher than the MCL have also been detected. It has been suspected that even very low traces of atrazine can have harmful health effects (Hayes et al, 2002).…”