Sonoran boa (Boa imperator) shedded skin. 40x magnification. Darkfield microscopy.

The Sonoran boa is a common pet snake species that occurs naturally in Central and South America. It is non-venomous and typically grows to be about 6-7 feet long, which is apparently “small” for a Boa. I was surprisign to photograph this skin in darkfield and notice that it looked blue! We don’t see many blue organisms in nature because blue pigment is very rare and this snake obviously does not have blue pigment in its scales so where did this image come from? Here is what I think might be going on: snake skin contains melanin, the same pigment that is found in human skin cells. The blue produced by these photos is likely the result of light scattering caused by my use of darkfield microscopy (a technique, in short, in which the light used to produce an image goes through the specimen at oblique angles rather than straight through) as well as light scattering due to melanin+pockets of air absorbing all wavelengths of visible light except for blue which is refracted and captured by my camera. This phenomenon would create an image that appears blue while the specimen itself is a dull brown and white. In addition, the substance that lubricates the area between the new skin and shedded skin of this particular snake may cause a “milky or blue” shimmer so maybe this lubricant plays a role in the color illusion that produced this photo.