Reptiles sans scales?

I absolutely love it when I learn something new about the world that makes me stop dead in my tracks in amazement that this new information before me is actually true. Today, I had exactly one of those experiences, and at the risk of looking like a dunce in front of my herpetologists friends (who presumably have heard all of this before?), I thought I'd share.

While I'm not a huge fan of intentional inbreeding of animals (a common way to propagate rare mutations in domestic populations), I have to admit that inbred animals can provide remarkable opportunities to tackle otherwise impossible questions regarding genetics, evolution and development. The immensely valuable understanding of mouse genetics is the first example of this fact that comes to mind, though I'm sure there are others.

Why are they so useful? Scientists are pretty much limited to working with testable hypotheses (e.g. candidates for the correct answer to a given question) - so if it isn't something you can experimentally disprove (e.g. show its the wrong answer to the question), then science can't really help you out very much. For example, science can't answer questions like "Would a dog-horse hybrid run faster than a wolf-donkey hybrid?" without comparing actual hybrids of this sort (which to my knowledge don't and very likely can't exist). Unfortunately, these hard-to-impossible to answer questions aren't all this silly and useless. There are, less ridiculous questions that are similarly difficult if not impossible to test.

One such question, up until a few decades ago, was "Why do snakes have scales?" I mean, really, to test any hypotheses about this question we'd need to find some snakes that don't have scales, which we all know is impossible, right?

Wrong... that little fact is the fantastic little tidbit of information I stumbled upon today. As it just so happens, we DO know a little bit about why snakes have scales, because there ARE snakes who lack them! Even better, this isn't the case of some bizarre recently discovered species, but naturally occuring mutations in otherwise scaled species - giving us very comparable experimental controls (e.g. normal snakes of the same species, possibly siblings, etc.)!

Back before I was born, there was some work done to test existing hypotheses on the function of scales in reptiles. By chance, a scaleless Pacific(?) Gopher Snake (Pituophis catenifer) was collected near Oakland, California in 1971. The results of this work (and the image below) can be found in the article: A Scaleless Snake: Test of the Role of Reptilian Scales in Water Loss and Heat Transfer by Paul Licht and Albert F. Bennett (1972).

Now, science loves replicated experiments - they provide opportunities to test the generality of theories and a means to "double check" the work of others. Too bad there aren't any more of these scaleless critters around... Oh, right, nevermind - there are! In fact, there are a number of examples of scaleless squamates - and some are being bred in captivity (not necessarily for the good of science, mind you - think "hairless cats"...)

A quick scan through the world of reptile breeders turns up a number of other scaleless (or nearly scaleless) species including scaleless Bearded Dragons (details here), this photo of scaleless adder, a few scaleless rattlesnakes, this video of a reptile breeder and his hybrid scaleless rat snake which I assume are derived from scaleless Texas Rat Snakes (presumably different individual here), and of course among the more populer species (which are bred in large numbers) we have the scaleless Ball Pythons, and rumors of scaleless corn snakes. Whew!

More examples of research on these scaleless critters are out there if you're interested. For example, work done by these researchers interested in the diversity of kinds of skin out there in the animal world used some of these scaleless individuals and published this article about scaleless Western Diamondback Rattlesnakes, which don't seem to have any beta-karotin in their skin, giving them their very soft texture. Other references can be found in this (incomplete) list of references from Chad Arment via herper.com.