USDA scientists and their collaborators have found that naturally-occurring compounds that are found on the skin of certain poison frogs can incapacitate and kill fire ants.
The red imported fire ant (Solenopsis invicta) damages crops, devastates small animal populations, and inflicts painful stings to livestock and to humans. To determine whether poison-frog alkaloids would kill fire ants, scientists at the USDA-ARS’s Center for Medical, Agricultural, and Veterinary Entomology (CMAVE) partnered with researchers at the Smithsonian Conservation Biology Institute and others from the National Institutes of Health.
“After finding that the frogs had unique alkaloids, NIH scientist John Daly, now deceased, began exploring possible medical applications of the compounds,” said Robert Vander Meer, research leader for CMAVE’s Imported Fire Ant and Household Insects Unit. “Over the years, scientists have identified and isolated about 900 alkaloids from the skin of poison frogs.”
Poison frogs, natives of Central and South America, do not produce alkaloids. Instead, they sequester them by eating ants (including fire ants), mites, millipedes, and other arthropods that produce these compounds, according to Vander Meer. He and his colleagues developed a bioassay to measure the toxicity of 20 poison-frog alkaloids, some of which were very effective in controlling fire ants, while others were not.
Alkaloids derived from mites and found on the skin of Central America’s poison frog, Oophaga pumilio, were more effective at incapacitating fire ants than the fire ants’ own alkaloids.
“Interestingly, this same frog has a varied diet of ants and mites,” Vander Meer said. “Mite-derived alkaloids have also been reported on O. pumilio’s skin, and these compounds were found to be highly effective at incapacitating S. invicta.”
Scientists are considering expanding their research to include mosquitoes. Earlier work published in the Proceedings of the National Academy of Sciences demonstrated that a poison-frog alkaloid called pumiliotoxin 251D was effective against the yellowfever mosquito (Aedes aegypti). Insects that landed on surfaces treated with the compound could no longer fly and died. In the future, poison-frog alkaloids or derivatives may prove useful in helping to control mosquitoes, according to Vander Meer.
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