Fearless frogs feast on deadly hornets

(Press-News.org) A remarkable resistance to venom has been discovered in a frog that feasts on hornets despite their deadly stingers. This frog could potentially serve as a model organism for studies on mechanisms underlying venom tolerance.

While just the sight of a hornet’s stinger is enough to fill many of us with dread, some animals, such as some birds, spiders and frogs, are known to prey on adult hornets. The venom injected by their stingers can cause sharp, intense pain as well as local tissue damage and systemic effects such as destruction of red blood cells and cardiac dysfunction, which may even be fatal. But whether the animals that hunt hornets are able to tolerate the venomous stings, or just manage to avoid them, has remained unclear. “Although stomach-content studies had shown that pond frogs sometimes eat hornets, no experimental work had ever examined how this occurs,” says Kobe University ecologist SUGIURA Shinji.

To test whether frogs avoid or tolerate these potentially deadly hornet stings, Sugiura presented individual adult pond frogs with workers of three hornet species, Vespa simillima, V. analis, and V. mandarinia, under laboratory conditions. Each frog was used only once, and was matched to fit the size of their prospective hornet prey, with larger frogs preferentially matched with Asian giant hornet (V. mandarinia) prey. 

In the journal Ecosphere, Sugiura submits striking evidence that adult pond frogs actively attacked workers of the three hornet species. What’s more, he also reports that 93%, 87%, and 79% of frogs ultimately consumed V. simillima, V. analis, and V. mandarinia, respectively, despite being stung into the mouth or even into the eyes. “While a mouse of similar size can die from a single sting, the frogs showed no noticeable harm even after being stung repeatedly. This extraordinary level of resistance to powerful venom makes the discovery both unique and exciting,” says Sugiura. 

Previous studies have suggested that pain and lethality of venomous stings are not necessarily correlated, with some stinging bees, wasps and ants delivering extremely painful, non-lethal stings while others cause little pain despite high lethality. This could mean that the frogs in this study have developed a double tolerance to these stings, which has enabled them to successfully prey on hornet workers.

 “This raises an important question for future work,” he adds, “namely whether pond frogs have physiological mechanisms such as physical barriers or proteins that block the pain and toxicity of hornet venom, or whether hornet toxins have simply not evolved to be effective in amphibians, which rarely attack hornet colonies.” These frogs could, therefore, also serve as valuable model organisms for studying the physiological mechanisms underlying venom tolerance and pain resistance in vertebrates moving forward.

This research was funded by the Japan Society for the Promotion of Science KAKENHI (grants JP23K18027 and JP24K02099).

Kobe University is a national university with roots dating back to the Kobe Higher Commercial School founded in 1902. It is now one of Japan’s leading comprehensive research universities with over 16,000 students and over 1,700 faculty in 11 faculties and schools and 15 graduate schools. Combining the social and natural sciences to cultivate leaders with an interdisciplinary perspective, Kobe University creates knowledge and fosters innovation to address society’s challenges.

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