African Frog Breaks Its Own Bones to Form Claws

African Frog Breaks Its Own Bones to Form Claws


A study of rare African frogs (Trichobatrachus Robustus) has revealed a form of self-defense previously unknown to the scientific world: claws of pure bone that burst through the frogs’ skin. And it gets worse. When the frogs are threatened they need to first “actively break” their own bones in order to create these claws.

This incredible defence mechanism is made possible by a number of adaptations. At rest, the claws are in a mass of connective tissue. One end of the bone is connected by a chunk of collagen to another small bone at the tip of the frog’s toe, while the other end is connected to a muscle. David Blackburn from Harvard University and his team believe that when the frog is attacked, this muscle contracts and the claw pierces the toe pad. Unlike other retractable claws, these claws are made of bone (rather than keratin, as is usually the case) and come straight through the skin.

African Frogs - Trichobatrachus Robustus (2)

The mechanism is unique among vertebrates, as is the fact that the claw is just bone – without an outer coating of keratin as other claws do. But only studied dead specimens have been studies, so it is unknown what happens when the claw retracts – or even how it retracts.

It does not appear to have a muscle to pull it back inside so it’s thought that it may passively slide back into the toe pad when its muscle relaxes.

Males of the species, which grows to about 11 centimetres, also produce long hair-like strands of skin and arteries when they breed.

The ‘hairs’ allow them to take in more oxygen through their skin while they take care of their brood.

24 Jun 2008, Washington, DC, USA --- The foot of a living Trichobatrachus robustus frog, which is one of the 11 species of African frogs, shows the white bony claws protruding from the tips of the toes in this undated handout photo. At least 11 species of African frogs carry a built-in concealed weapon -- they can sprout claws on demand to fight off attackers. --- Image by © Courtesy of Harvard University/Handout /Reuters/Corbis

Trichobatrachus Robustus is a super-hero in its own right, fighting for its life with its extendable weapons in the Cameroon jungle. The Bakossi people of Cameroon traditionally believed that the frogs fall from the sky and, when eaten, childless couples become fertile.

Hunters use long spears and machetes to kill the frogs, apparently to avoid being hurt by their claws.

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