Wednesday, December 03, 2025

Fearless frogs feast on deadly hornets

Kobe University

251204-Sugiura-Stings-Frog_eats_hornet — image:
Kobe University ecologist SUGIURA Shinji discovered that the black-spotted pond frog seems to be unharmed and undaunted by venomous stings from hornets such as the Asian giant hornet, the largest in the world.
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Credit: Shinji Sugiura, Ecosphere 2025 (DOI 10.1002/ecs2.70457)

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.

Journal

Ecosphere

DOI

10.1002/ecs2.70457

Method of Research

Experimental study

Subject of Research

Animals

Article Title

Pond frog as a predator of hornet workers: High tolerance to venomous stings

Article Publication Date

4-Dec-2025

The venomous stinger of an Asian giant hornet (Vespa mandarinia). The venom injected by this stinger 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.

Credit

Shinji Sugiura, Ecosphere 2025 (DOI 10.1002/ecs2.70457)

The black-spotted pond frog shows remarkable tolerance to venomous stings from an Asian giant hornet. The stings caused no visible harm and the frog behaved normally after predation. Close-up views of the hornet’s stinger embedded in the frog’s mouth are shown in the circular insets in (C) and (D).

Almost all frogs in the study attacked the hornets, and although the hornets stung the frogs repeatedly, 93%, 87%, and 79% of frogs ultimately consumed *Vespa simillima*, *V. analis*, and *V. mandarinia*, respectively.

Credit

Shinji Sugiura, Ecosphere 2025 (DOI 10.1002/ecs2.70457)

The ship-timber beetle's fungal partner: more than just a food source

How a symbiotic fungus helps a beetle survive in dead wood

Max Planck Institute for Chemical Ecology

image:
Maximilian Lehenberger with a culture of the ambrosia fungus *Alloascoidea hylecoeti* on an artificial medium.
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Credit: Angela Overmeyer, Max Planck Institute for Chemical Ecology

The ship-timber beetle (Elateroides dermestoides) is a species of ambrosia beetle. Unlike many of its relatives, which are social insects that live in colonies, it is solitary and does not live with other members of its species. While ambrosia beetles usually have generation times of less than a year, the next generation of ship-timber beetles does not hatch for up to two years. It is also one of the largest European ambrosia beetles, reaching lengths of up to 18 millimetres. Despite its solitary lifestyle, the ship-timber beetle does not live alone; it lives in a symbiotic relationship with the ambrosia fungus Alloascoidea hylecoeti, which provides it with nutrients.

First evidence of nutrient symbiosis with the ambrosia fungus

A team led by Maximilian Lehenberger from the Max Planck Institute for Chemical Ecology in Jena investigated this beetle-fungus symbiosis in more detail. To achieve this, the researchers first analyzed the nutrients accumulated by the fungus in its mycelium — the network of thread-like structures that make up its vegetative body. 'Until now, it was only assumed that ambrosia fungi were nutrient-rich. However, there was hardly any useful data to support this. In our study, we were able to demonstrate for the first time that Alloascoidea hylecoeti, in particular, is extremely nutrient-rich. This fungus accumulates many nutrients — significantly more than other fungi, both symbiotic and non-symbiotic — including sugars, amino acids, ergosterol, fatty acids, and the essential elements phosphorus and nitrogen,' says Maximilian Lehenberger, head of the Forest Pathogen Chemical Ecology (FoPaC) project group in the Department of Biochemistry. This probably also explains why the ship-timber beetle can live in nutrient-poor wood for so long and grow so large.

Surviving in a highly competitive environment

The larvae of the ship-timber beetle spend a relatively long time living in the wood of recently deceased trees. This environment is challenging for the offspring of the beetles, which can grow up to two centimeters long, because dead wood is very poor in nutrients and teeming with competition. In social ambrosia beetle systems, individuals can support each other by keeping harmful fungi at bay. This is not the case with solitary beetles. The research team therefore hypothesized that the symbiotic fungus has developed its own strategies to protect itself from competing species. They found that the fungal symbiont Alloascoidea hylecoeti uses various phenolic substances obtained from the surrounding wood. The fungus accumulates these substances to such an extent in its environment that it inhibits the growth of many other fungi. It uses its ability to grow into wood to access further resources. “Unlike many other fungi, the symbiotic fungus is neither broken down nor inhibited by plant defense compounds. Furthermore, it produces many substances that inhibit other fungi,” explains Maximilian Lehenberger.

A fungus that lowers the pH and grows even better in overly acidic environments

The scientists were particularly surprised by the production of acetic acid, which they detected in fungal cultures and samples from beetle nests using nuclear magnetic resonance (NMR) analysis. Experiments with fungal cultures revealed that the ambrosia fungus outcompetes other fungi by 'acidifying' its environment and lowering the pH to as low as 3.5. Remarkably, Alloascoidea hylecoeti not only copes with a very high concentration of acetic acid, but actually thrives at a pH level that is extremely low for fungi. "To date, acetic acid has not been detected in any other ambrosia beetle system. Since we were also able to identify acetic acid in the nests, this is clear evidence that it must play a role in nature too. The fungus utilizes not only acetic acid, but also a variety of other substances to inhibit competing fungi. These include monoterpenes such as linalool, terpineol and citronellol,' says Jonathan Gershenzon, Head of the Department of Biochemistry. Citronellol is responsible for the lemon-like smell of this fungus.

The impact of a highly acidic habitat on the larvae of the ship-timber beetle is unclear, as is the effect of the defensive substances that accumulate in the fungal biomass of their food source. Could this make them less attractive to predators? Could symbiotic bacteria in the beetles' guts help break down high concentrations of phenolic compounds? The research team plans to address these questions and others in future experiments.

Maximilian Lehenberger and Jonathan Gershenzon performing mass spectrometric analysis of substances.

Credit

Angela Overmeyer, Max Planck Institute for Chemical Ecology