Have you ever wondered
how a chameleon changes colors so rapidly? Cutting edge research reveals how
this color changing process actually works. After hearing our fellow classmate
talk about chameleon color change, and even hearing about it via social media,
I took it into my own hands to read the article that was published in the last
few weeks.
I have always assumed
that chameleons only change color in order to camouflage with their
surroundings, in hopes of avoiding predation. However, this article revealed another
reason for their spectacular color changing ability, which is to improve the
resistance to variable sunlight exposure. Unlike most lizards, the skin of a
chameleon has two thick layers of iridophore cells. Each of these layers
consists of guanine crystals of different shapes, sizes, and organization. The
upper layer of cells is referred to as the S-iridophore layer and has small,
close packed crystals. However, the lower, more flat and disorganized crystal layers
of cells are of particular interest, and are known as D-iridophores. Research
reveals that this larger D-iridophore layer that is extremely thick compared to
iridophores observed in other lizards, can actually reflect a large portion of
direct and indirect sunlight, even in the near-infrared range. This is important because many chameleons
occupy environments that are dry/arid, and exposed to intense sunlight.
According to this particular study, the D-iridophores cause a 45% decrease in
sunlight absorption. Considering the environment that many chameleons live in,
this ability of D-iridophores to provide a means for thermal protection is
likely highly advantageous for chameleon's survival.
S-iridophores, rather
than D-iridophores, are thought to aid in the rapid color change that occurs during courtship, and male-male interactions. Chameleons actively
change their guanine crystal spacing in the S-iridophore layer. For example, by
increasing the distance between crystals, S-iridophores can shift their
selective reflectability from blue to red wavelengths, which in response causes
a shift from green to yellowish orange skin color. I find it very interesting
that chameleons have the ability to both camoflauge, and also protect
themselves from intense radiation with the same kind of cells. I look forward
to hearing further research on this topic, and recommend that everyone reads this article if they get the chance.
Marel, D., Milinkovitch, M., Saenko, S., and Teyssier J.
(2015). Photonic crystals cause active colour change in chameleons. Nature Communications
1 comment:
Neat discovery!
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