A gram of venom from the Bruno’s casque-headed frog is enough to kill how many people?

Two Brazilian species are the world’s first known venomous frogs. They have tiny spines on their heads – particularly on their upper lips – that enable them to inject lethal venom into the bloodstream of an assailant.

A single gram of venom from the Bruno’s casque-headed frog (Aparasphenodon brunoi) would be enough to kill 80 people, or 300,000 mice. The frog’s venom is 25 times more poisonous by weight than that of a Brazilian pit viper. Venom from Greening’s frog (Corythomantis greening, pictured above) is less dangerous, but still twice as potent as a pit viper’s.

Edmund Brodie of Utah State University in Logan and his colleagues tested the potency of the venoms and scanned the frogs’ flesh, skin and skeletons. This revealed the spines on the faces of both species that take venom from neighbouring glands. Unusually for frogs, these species can wiggle and flex their heads up, down and sideways, injecting their venom by jabbing their spiny upper lips into their attacker’s flesh. This takes amphibian defences to a new level, says Brodie.