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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