Dr. Sara Broomhall
Position: PhD student
Year: 1998 - 2003
Short and Long-Term Effects of Temperature and Pesticides on Development and Fitness in Some Australian Anurans.
Contamination by agricultural chemicals continues to receive attention as a possible factor in amphibian population declines. It has been suggested that chemicals that do not appear to affect development or survivorship may render embryos and tadpoles more vulnerable to other exogenous factors such as parasitic or viral infections. Moreover, a natural stress (such as temperature) may alter how a chemical contaminant affects both target and non-target organisms. Existing research indicates that numerous biotic and abiotic variables can interact in an antagonistic, additive or synergistic manner.
Standard short term laboratory trials over one or a few days, such as those employed in acute toxicology testing, may not give insight into the longer term impacts on fitness of the study organism. Similarly, prenatal or embryonic exposure is often overlooked in toxicology studies, but has been shown to affect subsequent development in a number of species, including humans. The need for more biologically realistic and complex experimental scenarios is increasingly recognised in order to have an understanding of how agricultural chemical use may impact ecological communities.
My research aims to determine if short-term exposure to common pesticides may manifest in later alterations in tadpoles' behaviour and vulnerability to predation. Such correlates of fitness represent a step towards more biologically relevant experimental endpoints. I also aim to ascertain if embryonic rearing temperature may alter the developmental trajectory of the resultant tadpole, or modify its response to later thermal experience or to a sublethal chemical challenge.
Criteria for water quality guidelines are often based on the results of overseas laboratory studies. The relevance of these to Australian species - which are phylogenetically distinct and which also experience markedly different conditions - is questionable. Although endosulfan has been demonstrated to be toxic to Australian fish in low concentrations there appears to be a lack of published research on the effects of endosulfan on Australian anurans. Thus, I also aim to ascertain the effects that biologically realistic concentrations of endosulfan have on some Australian frog species.
To date, my results indicates that both embryonic rearing temperature and exposure to endosulfan can lead to alterations in behaviour and feeding rates. In some cases, tadpoles also subsequently manifested later variability to being captured by a natural predator. Thus, short-term exposure to endosulfan in natural conditions may also have the potential to manifest fitness effects or alter developmental trajectories long after cessation of actual pesticide exposure. Likewise, the conditions the tadpole experienced as an embryo may potentially alter the modes of action of some pesticides. Taken together, these data induce caution when considering potential long-term effects of early embryonic experience, and of possible fitness consequences of sublethal pesticide exposure.
Broomhall, S.(1998). The implications of ozone depletion for the Australian Alps: A review. inSnow: a natural history; an uncertain future.ed K. Green. Surrey Beatty & Sons, Chipping Norton. 224-247.
Broomhall, S., Osbourne, W. & Cunningham, R. (2000). Comparative effects of ambient ultraviolet-B (UV-B) radiation on two sympatric species of Australian frogs.Conserv. Biol.(In press).
Broomhall, S.& Shine, R. (2003). Effects of the insecticide endosulphan and presence of congeneric tadpoles on Australian treefrog (Litoria freycineti) tadpoles.Arch. Env. Contam.Toxicol.45:221-226.
National Conference of Frog Groups (WWF/RioTinto), Sydney, Australia.
Australian Society of Herpetologists Tasmania, Australia.
ASIH/SSAR/AES/NIA/HL/CAH La Paz, Mexico.
Global Threats to the Australian Alps Jindabyne, Australia.
Australian Society of Herpetologists Yungaburra, Australia.
National Threatened Frog Workshop Canberra, Australia.
ASIH/SSAR/HL/GIS/AES Seattle, Washington, USA.
Australian Society of Herpetologists Wellington Mills, Western Australia.