Cane toad toxic venom and pheromones
Project Leader: Prof Rob Capon, University of Queensland
Aim: To develop strategic knowledge on cane toad chemicals and ecology.
This project aims to approach the control of cane toads by exploring and understanding the chemical and ecology of cane toads, and to use this knowledge to develop strategies capable of enhancing the success of baiting and trapping programs.
Despite many prior studies, the chemical composition of cane toad toxin has not benefited from modern chemical analysis. Comprehensive chemical analysis is revealing classes of toxic molecules with potent and selective biological mechanisms of action.
This study aims to assess the full suite of toxic chemical constituents (small molecules, peptides, proteins, volatiles, involatiles, etc), as well as their natural occurrence against a range of variables including, sex (male versus female); fertility cycle; life cycle (tadpole – juvenile – mature); healthy versus stressed; season, ecosystem and geography.
Knowledge of the molecular structure and distribution of venom constituents, along with their mode of action, will reveal a selection of potential biological targets able to support the development of toad specific poisons.
- Alarm Pheromones: The only reproducible pheromone behavioural response that has been reported for the cane toad is the tadpole alarm pheromone. Preliminary investigations suggest that the alarm pheromone can be isolated and identified, and assessed as a potential cane toad control strategy.
- Bufadienolides: Cardiotoxic steroids, bufadienolides are common to many species of plant and animal, and are closely related to the cardenolides, with both compound classes displaying a common inhibition of the Na/K ATPase. Our studies have confirmed that the distribution of bufadienolides across the glands, organs and tissues of the Australian cane toad is quantitatively and qualitatively different from those reported in overseas cane toads. We have also demonstrated that the bufadienolide content varies significantly across life-stages, an observation that has particular significance with respect to toxicity. Our investigations have also revealed the Australian cane toad parotoid secretion contains not 4 but >100 bufadienolides, the majority of which remain unidentified.
- Alkaloids: Cane toad alkaloids are fast acting hallucinogens that target the central nervous system (CNS), and are very likely the true defensive chemicals deployed by adult cane toads, capable of confusing and distracting predators. Long overlooked by their more readily analysable bufadienolide cousins, the qualitative and quantitative distribution of cane toad alkaloids has received only cursory attention in the scientific literature, with no serious published analysis of their occurrence in Australian cane toads. We believe that cane toad alkaloids are a critical element in the defensive strategy, and play a pivotal role in the interactions between cane toads and Australian predators.
Prof Rob Capon, Professor Paul Alewood, Professor Gordon Grigg, Professor Richard Lewis, Dr Andrew Hayes, Alexis Barrett (University of Queensland).
IA CRC, University of Queensland.
Hagman M, Hayes RA, Capon RJ and Shine R (2008) Alarm cues experienced by cane toad tadpoles affect post-metamorphic morphology and chemical defences. Functional Ecology 23: 126-132.
Hayes RA, Barrett A, Alewood PF, Grigg GC and Capon RJ (2008). Chemical Signals in Vertebrates 11, Use of chemical ecology for control of the cane toad? Springer: 2008
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