Search for Frog Poison Crosses Globe, Species

After more than a decade of work, a California researcher thinks he has solved the 40-year mystery of where poisonous South American frogs get their deadly neurotoxin -- and surprisingly, the lead came from birds in New Guinea.

The poison has been used for centuries by indigenous Colombians to coat the points of their tiny blow darts, allowing them to bring down large prey -- as well as humans -- with relative ease.

Called batrachotoxin -- from the Greek batrachos, or frog -- the lethal agent is 10 times as deadly as the tetrodotoxin from the puffer fish. Simply handling the frogs that secrete it from their skin can be fatal.

Ornithologist John P. Dumbacher of the California Academy of Sciences in San Francisco and his colleagues reported this week in the Proceedings of the National Academy of Sciences that the ultimate source of the poison was most likely little-studied beetles in the Melyridae family.

The discovery is of more than academic interest, because batrachotoxin is widely used in studying the function of sodium channels -- gates in the cellular membrane that are implicated in a variety of diseases, including multiple sclerosis.

Those who work with the toxin must get it from the National Institutes of Health, which collected a small supply 25 years ago. That supply is running out, and researchers cannot collect more in Colombia because of political turmoil there. The discovery could lead to new ways to collect the useful poison.

Dumbacher got a lead in 1992, when he heard from people in New Guinea about a bird called a pitohui that caused numbing or burning sensations when eaten. He ultimately found batrachotoxin in five species of pitohui.

Elders in the tiny New Guinea village of Herowana told team members about a beetle they called nanisani that produced numbing or tingling sensations when touched.

Samples of the beetles, of the Choresine genus of the Melyridae family, were collected for the scientists, who analyzed them and found the toxin. They also found the remains of the beetles in the birds’ stomachs.

Significantly, Melyridae beetles are also found in Colombia.

Dumbacher cautioned that the team was not sure that the beetles produced the toxin; they might collect it from a plant instead.

That might be better in the long run, he added, because a plant would be easier to grow in the laboratory.

Either way, a new source of the toxin appears to be just over the horizon.