BRIEF: The Bug That Can Survive A Toad’s Stomach

(Inside Science) -- With a flick of its tongue, the toad snags a snack. But this meal is a bombardier beetle, famous for its explosive weaponry. Upon being swallowed, the beetle unleashes a blast of poison as hot as boiling water. At first, the toad appears unperturbed. After 44 minutes, however, it relents. Back out comes the bug, soaked in mucus.

It’s still alive.

The beetle in question survived attempted digestion in May 2016, in the lab of Shinji Sugiura and Takuya Sato of Japan’s Kobe University. Researchers have seen animals such as snails and snakes survive trips through the digestive systems of predators before. But no one has ever reported a forced vomiting of an ingested bombardier beetle, Sugiura said. And not much is understood about the ecological factors that determine survival.

Now in new experiments, published today in the journal Biology Letters , the researchers placed individual bombardier beetles, Pheropsophus jessoensis, in a tank with one of two toad species, Bufo japonicas and Bufo torrenticola. The toad always swallowed the beetle. In 43 percent of the trials, though, the beetle forced the toad to puke it out. All the vomited bugs survived -- even, sometimes, after more than an hour and a half inside the toad.

Larger beetles, which can discharge more toxins, escaped more often than smaller ones. Smaller toads also vomited more often than bigger ones.

And the beetle is tough. The researchers inserted beetles through the toads’ mouths, and then, after 20 minutes, flushed the toads’ stomachs with water to see if the bugs survived. More P. jessoensis survived than other beetle species.

But the researchers aren’t sure how. Perhaps P. jessoensis has a high tolerance for digestive juices. Or, perhaps its chemical defenses weaken those juices.

As for the toads, they’re fine -- if a bit hungry.