Amid agony, scientists discover world’s first venomous frog

Carlos Jared

Amid agony, scientists discover world’s first venomous frog

Brazilian biologists have discovered the world’s first venomous frog the hard way.  When Carlos Jared of the Butantan Institute in São Paulo, Brazil, picked up a Brazilian hylid frog (Corythomantis greening, pictured)—a small, lumpy, green amphibian—while doing fieldwork in a jungle in the Goytacazes National Forest near the southwest coast of Brazil, the frog raked the spines hidden within its upper lip across his hand. He dropped the frog, and excruciating pain shot up his arm for the next 5 hours. Several other species of frogs are poisonous, but until now none have been shown to be venomous—that is injecting a toxin into their host. C. greening’s venom is twice as potent as that of the deadly pit viper, the researchers report online today in Current Biology. The team found another venomous Brazilian hylid frog, Aparasphenodon brunoi, also in the Goytacazes National Forest. Its venom was a whopping 25 times more deadly than that of a pit viper, but this time the researchers were smart—they didn’t pick it up. Both frogs deliver their venom from head spines resting in toxic glands in their skin. When the animals attack, the skin contracts and the poison-coated spines protrude from the frog’s lip. Researchers imagine as a hungry predator closes its mouth over the frog, it begins shaking its head and jabbing the spines into every corner a frog’s face can fit. These two frog species are not very closely related, so researchers think several more frogs could have evolved to be venomous. It’s possible the adaptation evolved multiple times in the perilous rainforests, but scientists just never picked up on it.

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