This frog just cAN'T be bothered: Frog species has chemical skin secretions that prevent attack from leaf-cutting ants

The article "The frog Lithodytes lineatus (Anura: Leptodactylidae) uses chemical recognition to live in colonies of leaf-cutting ants of the genus Atta (Hymenoptera: Formicidae)" was written by André de Lima Barros, Jorge Luis López-Lozano, & Albertina Pimentel Lima and published in Behavioral Ecology and Sociobiology in late 2016. The researchers studied the chemical mechanisms used for inter specific communication by a species of Amazonian frog to two species of leaf cutter ants. Liithodytes lineatus uses the nests of the leaf cutter ants for shelter and breeding, without being attacked by the ants. The ability of these frogs to prevent attack from the ants was unknown until the study. The researches did know, however, that the ants use chemical secretions to identifiy members from the same colony and hypothesized that the frogs produced a chemical similar to the one that the ants used for identification.

To conduct their study, the researchers collected 10 individuals of L. lineatus and 20 individuals from 4 other local frog species. They placed each individual at the entrance of an ant nest and placed a clear topless glass box around them. They waited 10 minutes, removed the frog, and counted how many ants were on the individual. They also recorded how long it took for the first ant to bite the frog. They also took skin samples from L. lineatus and made extracts with them. They then took an abundant local frog known for absorbing liquids into their skin (Rhinella major) and immersed them in the skin extract or in ultrapure water. They attached these frogs to a string, placed them at the entrance of the ant's nest, waited 5 minutes, and then counted the number of ants that had bitten onto the frog.

The researchers found that L. lineatus received significantly fewer bites from ants (close to 0) than all other species tested (Figure 1). The time taken for the ants to bite was also significantly shorter in species that were not L. lineatus (less than two minutes compared to 10) (Figure 2). The skin extract tests also resulted in data that supports the idea that L. lineatus produces skin chemicals that mimic the ants to prevent them from biting. Frogs with the skin extract on them had far fewer ant bites than those who were just sprayed with water (Figure 3). The frogs with the skin extract also went under a much longer response time from the ants than did the frogs with ultrapure water (Figure 4).

The research produced in this study confirmed that L. lineatus is unique in its ability to associate closely with ants that otherwise attack frogs in their nests. This species of frog did not try to escape during the experiments, as opposed to all other species of frog tested. They proved through the skin extract portion of the experiment that it is a chemical in strictly the skin of the organism that prevents it from being attacked. Further research must be done to determine which chemical in the skin specifically prevents the attacks, but this study confirmed a very interesting hypothesis about a novel behavior in the frog species L. lineatus. Though most frogs do not closely associate with insects, there are exceptions. It is still unknown what kind of relationship these frogs have with ants, be it parasitic, mutualistic, or commensal.

This study was very interesting but I wish the researchers had done a bit more observational research to confirm the exact relationship between the ants and the frogs.


Click HERE for a link to the PDF of the article