The X-Man Wolverine has never been one of my favorites. Maybe it’s because it didn’t seem fair. Most mutants only get one ability, but he got two: an impossibly potent healing factor and retractable bone claws that are housed in his forearm. The latter seems to require the former or he would run the risk of infection and severe loss of blood every time he popped his claws out.
Wolverine (c) Marvel Comics, artwork by Frank Miller. Image: Gustavocarra / Creative Commons License
In terms of a “healing factor,” The Field Guide to Super-Powers is replete with examples. Most of us are familiar with reptiles and amphibians that can regenerate lost tails and limbs. There’s even a newt (Notophthalmus viridescans) that can regenerate a lost an eye, for Pete’s sake. We’ll discuss some choice invertebrates below that also regenerate bits and pieces they’ve lost. So, healing factor identified in nature. Check. Let’s turn our attention to those ridiculous…er…fascinating claws.
Wolverine’s bony claws are housed in his forearm and pop out of his knuckles. As an added bonus, some really bad people coated the claws and all of his bones with unbreakable adamantium so these babies can cut through anything. What makes the ability particularly strange (and I realize we left strange behind some time ago, but bear with me) is that it requires Wolverine to do some self-inflicted damage since those claws must pierce his skin each time they are deployed. Obviously, he can handle it since he has the healing factor. But surely self-inflicted wounds don’t happen in nature, right?
In fact, there are a number of examples of critters that will do bodily harm to themselves if the circumstances are dire enough. Sea cucumbers will eviscerate themselves and sea stars will jettison an arm to evade predators. Both, of course, can regenerate what was lost, so these are extreme but survivable, measures. They are also dependent on their respective “healing factors.” Now I know what you’re saying: These are last ditch defensive measures. Surely, SURELY, routinely popping bones out of your skin as a weapon makes no sense at all in nature.
Except, of course, it does, when it provides a selective advantage. Case in point: African frogs of the genera Astylosternus and Trichobatrachus. I spotted these creatures as I was wandering around Cameroon (O.K., David Blackburn made the actually discovery, but I did stumble across this as I was browsing through an old National Geographic a couple of weeks ago in my easy chair). When disturbed, these frogs deploy a bony claw from the tip of its toe. The claw is usually held in place by a stationary claw rest. To use it, a tendon pulls the claw from its resting position and the tip of the curved bone pierces the skin. Snikt!
A bad attitude seems to come along with claws like these (it probably stings a little for the frog and Wolverine). When disturbed, these frogs apparently flip out, kicking and squirming in an attempt to inflict as many gashes as possible on their attacker. As the researchers who described this adaptation point out in Biology Letters, this is a truly unique adaptation. No other vertebrate has to pierce its own skin to use its claws.* Fortunately, the self-inflicted wound that results from their use is probably no big deal for the frogs since, like many amphibians, they do have that remarkable ability to regenerate tissues.
National Geographic (June 2009), Wildlife, page 22
* This is a unique claw, but other amphibians pierce their skin with other bones. When threatened, the ribbed newt Pleurodeles waltl can project poison-tipped ribs from their back.