Monday 11 June 2018

Toxic toad invasion puts Madagascar's predators at risk, genetic evidence confirms



June 4, 2018, Cell Press

The recent introduction of the common Asian toad to Madagascar has led to fears that the toxic amphibian could wreak havoc on the island's already severely threatened fauna. Now, researchers report genetic evidence in the journal Current Biology on June 4 showing that those fears are well founded: virtually all predators native to Madagascar are highly sensitive to toad toxins. If they should eat the toads, it would be a potentially fatal mistake.

"In Australia, the introduction of cane toads has caused profound perturbation to many ecosystems by removing key predators from local food webs with their toxins," says Wolfgang Wüster of Bangor University, United Kingdom. "Similar effects are likely to occur in Madagascar, where toads were never present before, as well; predators that frequently feed on toads and do not rapidly learn or evolve to avoid them are likely to become much rarer or possibly extinct."

Bufonid toads secrete bufadienolides that kill many predator species by inhibiting the sodium-potassium pump (Na+/K+-ATPase), an essential component of animal cell membranes. However, some species are known to have evolved resistance to these toxins through repeated, predictable, and specific point mutations in the gene encoding that essential enzyme. As such, the arrival of the toxic and invasive Asian toads (Duttaphrynus melanostictus) to Madagascar prompted vigorous debate over their likely impact and the actions that should be taken to control or eradicate them.



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