Horror Frog

Of all the frogs in the world, perhaps the strangest named one is the horror frog!  It’s real name is Trichobatrachus robustus .   Would you believe that this frog actually breaks its own bones, more than likely when it is feeling threatened by someone or something,  and these broken bones produced claws that break through the frog’s toe pads.  Isn’t that grisly!   


Apparently there are some salamanders that also behave in this gruesome way, as they force their ribs through their skin to produce protective barbs.  And it is thought that nine out of the eleven frogs that belong to a group known as Astylosternus also feel compelled to act in this very bizarre way!  Most of these are native to Cameroon. 


There are some frogs that naturally have bony spines that protrude from their wrists, but this is something different as they are there already and are not made on demand as it were, as is the case with the horror frog.


When the T. robustus  is resting, the claws found on the hind feet only, are nestled inside a mound of connective tissue. A lump of collagen forms a bond between the claw's sharp point and a piece of bone at the tip of the frog's toe.

The other end of the claw is connected to a muscle. It is felt by experts that when the frog is attacked, it tightens 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.  The end result may look like a cat's claw, but the breaking and cutting mechanism is very different and unique among vertebrates. Also unique is the fact that the claw is just bone and does not have an outer coating of keratin like other claws do.

Unfortunately, experts are not sure yet 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 the general thought is that it may passively slide back into the toe pad when its muscle relaxes.  This is not known for sure, as most of the investigation done on these horror frogs have been carried out on dead frogs.  And as amphibians it would not be surprising if some parts of the wound heal and the tissue is regenerated.

Males of the species, which grows to about 11 centimetres, also produce long hair-like strands of skin and arteries when they breed  as shown in the photograph.  It is thought that the "hairs" allow them to take in more oxygen through their skin while they take care of their brood.

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

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