|Weldon, Paul J|
|Vander Meer, Robert - Bob|
|Hoffmann, Wesley - Clint|
Submitted to: Naturwissenschaften
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/7/2013
Publication Date: 1/23/2013
Citation: Weldon, P., Cardoza, Y.J., Vander Meer, R.K., Hoffmann, W.C., Daly, J.W., Spande, T.F. 2013. Contact toxicities of Anuran Skin Alkaloids against the Red Imported Fire Ant (Solenopsis invicta). Naturwissenschaften . 100:185-192. Interpretive Summary: Nearly 500 alkaloids, representing over 20 structural classes, have been identified from the skin of poison dart frogs. These surface compounds are derived from leaf-litter arthropods, including ants, eaten by the frogs, and are generally believed to deter predators. To test whether or not these alkaloids are deterrents to predatory ants, scientists from the Imported Fire Ant and Household Insect Unit at the Center for Medical, Agricultural and Veterinary Entomology, USDA, ARS, Gainesville, FL; Southern Plains Agricultural Research Center, ARS, USDA, College Station, TX; Smithsonian Conservation Institute, Front Royal, VA; North Carolina State University, Raleigh, NC; Laboratory of Bioorganic Chemistry, National Institute of Diabetes and Digestive and Kidney Diseases, NIH, Bethesda, MD, developed a sensitive bioassay to measure the contact toxicity of 21 poison dart frog alkaloids to fire ant workers. The results demonstrate that the alkaloids are toxic and can therefore play a role in defending the frogs from arthropod predators including fire ants that do overlap with the natural distribution of the frogs.
Technical Abstract: Nearly 500 alkaloids, representing over 20 structural classes, have been identified from the skin of poison frogs (Dendrobatidae). These cutaneous compounds, which are derived from leaf-litter arthropods eaten by the frogs, generally are believed to deter predators. We tested the red imported fire ant (Solenopsis invicta) for toxicosis following contact with 21 alkaloids (12 structural classes) identified from dendrobatids or other anurans. Individual ants forced to contact the dried residues of 13 compounds exhibited convulsions and/or reduced ambulation. We estimated the cutaneous concentrations of select compounds based on their reported recoveries from skin extracts of free-ranging frogs and our estimates of the skin surface areas of museum specimens. Pumiliotoxin 251D exhibited contact toxicity well below its estimated cutaneous concentration in the Ecuadorian frog, Epipedobates anthonyi, an observation consistent with the hypothesized role of this compound in anuran chemical defense. Our results and those of a previous study of mosquitoes indicate that some anuran skin compounds function defensively as contact toxins, permeating the exoskeleton of offending arthropods.