This month an exciting herpetological discovery has been made regarding amphibians and their defence mechanisms. While a variety of amphibians are known to secrete toxic substances, scientists have just discovered two species of venomous frog in Brazil which utilise a unique technique to dispense venom – bony horns located on their heads are capable of injecting toxins directly into other animals. The discovery was made by a collaborating team of scientists from the Butantan Institute in São Paulo, Brazil (pictured, above) and the University of Utah in the USA.
To understand the significance of this discovery it is important to first clarify the distinction between ‘poisonous’ and ‘venomous’. Venomous animals such as snakes utilise a form of active defence, where glands containing the venom are in communication with the teeth. When they attack, the muscle compresses the gland causing the venom to be released into the victim. On the other hand, amphibians have, up until now, been referred to as poisonous animals defined by their passive defence mechanisms. Their toxins are also secreted from glands but they lack a method of injection – predators are only affected if they come into direct contact with the toxin on the skin of the animal.
Brazil’s Venomous Frogs With Horns
In light of this distinction, the discovery of two species of venomous frogs, with the ability to inject venom using horns located on their head, is one that has brought a lot of excitement to the herpetological community. The two species in question are Corythomantis greeningi (Greening’s frog) found in the Caatinga savannah, and Aparasphenodon brunoi (Bruno’s casque-headed frog), found in Brazil’s Atlantic Forest.
This first of its kind discovery was made when Corythomantis greeningi drew the close attention of scientist Carlos Jared of the Butantan Institute. After handling the species during field work in the caatinga of Rio Grande do Norte, Jared experienced an intense pain in his arm lasting more than five hours. The intensity of the pain was such that Jared was sure he had contracted septicaemia, however upon medica
l examination it was revealed that the cause of the pain was in fact not a blood infection but rather the result of the venomous frog.
Extremely Poisonous Venom
According to another author of the study, Edmund Brodie of the University of Utah, Jared was lucky that the discovery was made as a result of being injected by Corythomantis greening and not by Aparasphenodon brunoi – the toxin released by A. brunoi is comprised of alkaloids and has a potency so strong that as little as 1g of the toxin is enough to kill 300,000 mice, or 80 humans!
More pictures of the Greening’s frog can be seen by clicking the link.
Full details of the study can be found in the scientific journal Current Biology.
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