typically thought of as male hormones but they have impor-
tant roles in both sexes.
Testosterone is an androgen, and a reduction in its activity
can cause many reproductive defects, including reduced fertility
and hypospadias. Hypospadias is a condition caused by a failure
of urethral closure during penis development, and is one of the
most common human birth defects in Australia, currently
affecting approximately one in every 125 live male births. Anti-
androgenic exposure in developing marsupials also causes mild
to severe forms of hypospadias. In the wild, severe hypospadias
would lead to infertility and increased risk of infections.
The potent anti-androgen atrazine is one of the most widely
used herbicides in Australian agriculture, with over 116 tonnes
released into the environment each year. Atrazine causes major
reproductive abnormalities in vertebrates, from frogs to rats and
humans. This chemical is a widely used herbicide for the control
of weeds in maize, sorghum, sugarcane, timber plantations,
lucerne, grass seed crops and potatoes. Atrazine is also used for
weed control prior to planting and for fallow maintenance. All
such agricultural areas are home to many marsupial species, which
graze in high numbers on the treated crops and drink from irri-
gation channels and dams surrounding these areas.
In addition to atrazine, diazinon and dichlorvos are another
two pesticides currently used in Australia with known anti-
androgenic effects. Many others exist.
Thus, our native fauna are currently developing in an envi-
ronment surrounded by endocrine-disrupting chemicals but
we don’t have a full understanding of their potential impacts
on species fitness and survival.
One of the biggest concerns is the potential long-term
effects that EED exposures can have on fertility. Studies in
humans and mice exposed to large amounts of endocrine
disruptors during development have shown that the indi-
viduals have decreased fertility and reproductive abnormali-
ties as well as an increased risk of developing reproductive
cancers.
In addition, the offspring of individuals who were exposed
to EEDs also experience greatly increased rates of reproduc-
tive abnormalities and reproductive cancers. Many groups
are now examining the potential for endocrine disruptors to
alter our DNA’s epigenetic code in ways that might cause
defects to persist for multiple generations.
Thus there is a critical need to determine how severe the
impacts of different EEDs might be in different marsupial
species. Such research is absolutely critical to defining the
potential impacts of EED chemicals on the sustainability of
our native mammals and in the development of management
policies for the use of such chemicals in our environment.
Andrew Pask is an ARC Future Fellow and Associate Professor and Reader in the School of
BioSciences at The University of Melbourne.JAN/FEB 2016|| 37These hormonal alterations
can have a profound effect
on sex determination,
causing sex reversal in some
cases and reduced fertility.davemhuntphoto/Adobe