Long-term maternal exposure to atrazine in the drinking water reduces penis length in the tammar wallaby Macropus eugenii

Abstract

Marsupials are experiencing devastating population declines across Australia. Exposure to environmental endocrine disruptors, through ingestion of contaminated resources in the environment, could be contributing to this decline. Atrazine (ATZ), a widely used herbicide in Australia, is an endocrine disruptor with the ability to cause reproductive abnormalities in a diverse range of vertebrates. We exposed adult female wallabies (Macropus eugenii) to drinking water containing ATZ (450 p.p.m) throughout pregnancy, parturition and lactation. We assessed the outcome of this exposure to the reproductive development of their young by assessing gonad and phallus development. Both these organs are especially sensitive to perturbations in the hormonal environment during development. Although no gross abnormalities were seen in gonad structure, exposure to ATZ did alter the expression of genes required for normal testis function. Furthermore, long-term exposure to ATZ resulted in a significant reduction in penis length. These results demonstrate that ATZ exposure during gestation and lactation can significantly affect the development of male young by affecting virilisation. Given the known vulnerability of macropodid marsupials to endocrine disruption, as well as their overlapping distribution with agricultural areas, these data raise major concerns for the use of pesticides in areas with fragile marsupial populations.