Mosquito Repellent in Frog Skin Secretions
Frogs also excrete substances through their skin that protect them from mosquito bites. In laboratory tests, however, these showed only half the effectiveness compared to the widespread mosquito repellent diethyl(-m-)toluamide (DEET).
Craig Williams of James Cook University in Cairns and his colleagues shocked frogs of various Australian species with gentle current pulses and washed off the resulting skin secretions with distilled water. They then brushed the tails of mice with this solution before releasing eighty blood-hungry mosquitoes on the rodents. The researchers recorded the time until the first mosquito bite.
While a 10 percent DEET control solution protected the animals for up to two hours, secretions from the tree frog Litorea caerulea delayed the first sting for at least fifty minutes. The substances of other frogs had little effect.
However, the scientists suspect that their sampling procedure may have weakened the mosquito repellent effect, as other studies also showed that volatile substances caught in water had a lesser effect than when they were taken directly from cotton balls became. In addition, the animals in captivity could have reduced their production of mosquito repellent, since on the one hand the mosquitoes and on the other hand the necessary components of the food may be missing. Mosquito bites can also transmit parasites and pathogens to frogs.
