A research paper published in the journal Current Biology has explained about two species of frog that protect themselves by injecting their venom directly from their heads into predators. Corythomantis greeningi and Aparasphenodon brunoi are the frogs that can deliver the venom.

Study's lead researcher Carlos Jared from the Butantan Institute in Sao Paulo was of the view that the frogs have bony spines on their heads that deliver the venom. The researchers said this feature makes them the first venomous species of frog in the world.

The researchers discovered these frogs when Jared injured his hand due to the bony spines on the head of the Corythomantis greening that lives in savannas in eastern Brazil. Study's co-author Edmund Brodie from the Utah State University in Logan said the accident seems to have proved lucky as the frog that injured Jared was found to be less toxic of the two.

More toxic frog species is Aparasphenodon brunoi and its single gram of the venom could kill more than 300,000 mice or around 80 humans. To talk about Corythomantis greening, it could take lives of more than 24,000 mice or around six humans.

"Amphibians have a wide array of skin toxins that have been well-studied, but this sort of mechanism -- transmitting the toxin as venom -- has not been found before. It moves the study of amphibian defenses to a new level", affirmed Brodie.