The frog that breaks its own bones to produce claws that burst through its skin as weapons... just like X-Men's Wolverine

The Cameroon frog is unique as the claw is just bone without an outer coating of keratin, as other claws do

Scientist say that the frog’s flesh heals itself after the talons puncture the skin

A local tradition believes that when eaten, childless couples become fertile

Cameroon is home to a bizarre creature, Trichobatrachus robustus, that’s straight out of a sci-fi or horror film.

The bizarre, hairy frog with cat-like extendable claws can break its own bones to produce talons that puncture their way out of the frog’s toe pads.

David Blackburn and scientists at Harvard University's Museum of Comparative Zoology, think the gruesome behaviour is a defence mechanism.

Party trick: Hairy frogs from the Cameroon have revealed a remarkable mechanism that causes thorn-like claws to burst through the skin when it is threatened

The researchers say there are salamanders that push their ribs through their skin to produce protective barbs on demand, but the mechanism on this frog has never been seen before.

The feature is also found in nine of the 11 frogs belonging to the Astylosternus genus, most of which live in Cameroon .

'Some other frogs have bony spines that project from their wrist, but in those species it appears that the bones grow through the skin rather than pierce it when needed for defence,' Blackburn told New Scientist.

The claws of T. robustus, which are found only on the hind feet, are nestled inside a mass of connective tissue. A chunk of collagen forms a bond between the claw's sharp point and a small piece of bone at the tip of the frog's toe.

The other end of the claw is connected to a muscle. Researchers believe that when the animal is under threat, it contracts this muscle, which pulls the claw downwards.



The sharp point then breaks away from the bony tip and cuts through the toe pad, emerging on the underside.

Thorny problem: 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

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.

'Being amphibians, it would not be surprising if some parts of the wound heal and the tissue is regenerated,' says Blackburn.

Cutting edge: Wolverine, played by Hugh Jackman, has retractable claws. He also has a healing factor that allows him to recover from virtually any wound, disease, or toxin at an accelerated rate

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.

In Cameroon, they roasted and eaten. Hunters use long spears and machetes to kill the frogs, apparently to avoid being hurt by their claws.

‘This is an incredible story,’ says Ian Stephen, curator of herpetology at the Zoological Society of London, UK.

'Some frogs grown spines on their thumbs during breeding season, but this is entirely different.



‘For me, it highlights the need for a lot more research on amphibians especially in light of the threat of mass extinctions,’ he adds.

The existence of frogs with erectile claws like cats was first described by Belgian zoologist George Boulenger in 1900 in frogs found in the French Congo, now the Republic of Congo.

David Cannatella, a herpetologist at the University of Texas, Austin, questions whether the bony protrusions are meant for fighting. They could allow a frog's feet 'to get a better grip on whatever rocky habitat they might be in,' he says

The Bakossi people of Cameroon traditionally believed that the frogs fall from the sky and, when eaten, help childless human couples become fertile.