Chapter 1, The Reptilian Spectacle - UWSpace - University of ...

carpet python and western diamondback rattlesnake or predominantly acidic as in the spectacles of
coachwhip snakes.
The spectacle scale of hatchling reticulated pythons, representing the embryonic stratum
corneum, contains a larger ß keratin not found in the adult and also have a much lower proportion of α
keratin. It has been shown that the stratum corneum of hatchling snakes have a particularly thin mesos
layer which nearly doubles in thickness after the first shed (Tu et al. 2002). This is thought to increase
the efficacy of the water permeability barrier, which is not altogether necessary in the fluidic
environment of the egg, but is absolutely essential upon hatching, especially in arid and semi-arid
environments inhabited by the subject snakes of Tu et al.’s study (the California kingsnake,
Lampropeltis getula). This increase in the the ratio of α:ß keratin would explain the low α keratin
signal in the hatchling reticulated python. The difference in ß keratin complement is unclear. While the
hatchling spectacle scale’s spectral transmission varies slightly after the first shed (see Chapter 3), it is
not likely enough to affect vision. The biochemical difference may not be exclusive to the spectacle
scale and may be again for permeability or for necessary mechanical properties of scales in ovo.
4.4.3 Keratins of Gecko Scales
Gecko spectacle scales appear to be composed exclusively of α keratin. Being generally softer than ß
keratin, this explains the relative ease with which the spectacles are damaged. And although this study
does not conclusively relate biochemical composition with transparency, the absence of any ß keratin
may conceivably be cause for the gecko spectacle’s exceptionally high spectral transmission.
This absence also speaks to the modest need for mechanical protection of the eye in these
arboreal animals. Unlike snakes that may use their heads to persistently penetrate substrates or that
need to withstand potential retribution from large prey items, the eyes of arboreal geckos rarely
encounter anything more harmful than a speck of dust or the occasional collision during their rapid and
seemingly reckless locomotion. Nevertheless, any damage to the delicate surface risks damaging the
underlying mesos layer. This layer is normally well shielded by the hard beta layer, but in the gecko
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