A frog found in the Amazonian rainforest is able to perfectly impersonate leaf-cutter ants in order to trick them into not biting it, thanks to a chemical secreted by its skin, according to a new study. This allows the frog – known as Lithodytes lineatus – to intrude on the ants’ nest and lay its eggs, using the viciously defensive insects as bodyguards that attack any predators that may approach.
Living up to its reputation as evolution’s laboratory, the Amazon is full of creatures with remarkable adaptations that help them either to avoid predation or to kill. Many parasitic invertebrates, for example, produce chemicals that mimic those of their hosts, enabling them to disguise themselves as their prey and sneakily make contact.
Though this technique is rarely seen in invertebrates, researchers from the National Institute of Amazonian Research in Brazil began to suspect that Lithodytes lineatus may secrete chemicals that are similar to the pheromones used by leaf-cutter ants to communicate, after noticing that the frogs are never bitten by the ants when they enter their nests to lay eggs.
They therefore decided to place Lithodytes lineatus and four other Amazonian frog species in a glass container with some leaf-cutters ants, and noticed that while Lithodytes lineatus remained completely calm, all the other frogs panicked and tried to escape the vessel.
In the meantime, the ants brutally attacked all frogs apart from Lithodytes lineatus, which did not receive a single bite.
Next, the researchers coated 20 Rhinella major frogs with a chemical obtained from the skin of Lithodytes lineatus, and found that this caused the ants to completely ignore them. In contrast, all Rhinella major frogs that were coated only in water were savagely set upon by the leaf-cutters.
Publishing their study in the journal Behavioral Ecology and Sociobiology, the authors conclude that their experiments reveal that Lithodytes lineatus secretes a chemical that tricks leaf-cutting ants into thinking it is one of their own. "It helps the frog blend in, because it imitates the ants own chemical signals," said researcher André Barros in a statement.
As well as taking advantage of the fact the ants fend off predators that might otherwise eat its eggs, the frog also benefits from the humidity inside the nest, which the researchers say helps it reproduce.