Where’d the Blue Indi-go?

There is a color rarely found in living things that many usually associate with nature. We see it in the sky and the ocean, but not much else. Only a handful of animals are predominantly blue, there are no blue dogs or cats or squirrels. Why is this pigment so rare in the wild? Scientists aren’t completely sure yet, but their theories “blue” my mind and they should be shared.

To understand why blue pigment is so uncommon, we have to first understand what pigments are. According to the Encyclopedia Britannica, they are substances that an animal produces thats reflects a color based on selective absorption. Animals do not make red orange yellow or brown pigments from scratch, they’re created from ingredients in our diet. (Like how flamingos turn from grey to pink by ingesting red crabs and shrimp). The only known animal to make blue pigment is the Olivewing Butterfly, who has a strip of light blue on its wings. Scientists aren’t exactly sure how this and only this species evolved the pigment pterobilin/a> but it helps the species ward off predators and attract mates.

So if almost no animals make blue pigment, why do animals like Peacocks or Blue Morpho Butterflies (pictured) appear blue? The secret lies in the structures of their cells. If we were to zoom into a butterfly’s wing, we’d see thousands of scales, similar to those of a fish. In Blue Morphos, the structure of these scales look like tiny Christmas trees that trap all colors of light except for blue, which reflects into out eyes. This reflective property makes these wings iridescent, but it is all caused by light’s bending as it moves from air to another material. If you pour alcohol on these wings, the blue would disappear and we would see the greenish pigment the butterfly produces instead as the light doesn’t bend in the same way. Bird feathers contain much less organized bead structures that trap light, but again, this is because of the structure of the cells not pigment. Even blue eyes are a result of the cell structures inside of us.

Why haven’t animals evolved to make blue pigments, but can make blue causing structures? Scientists are still figuring this one out. One theory is that birds and butterflies evolved the ability to see blue but had no way of “painting” their bodies that color, which would prove beneficial for communication and survival. Creating a blue pigment would require these animals to take on a new chemistry, but evolution favored changing the structure of their bodies slightly to reflect blue light rather than make blue itself.

Perhaps scientists will find a way to mimic these structures so that we can color all sorts of things like cars or clothes without pigments. But for now, we’re stuck with our dyes and paints, blue-hoo.

About Mr. Mohn

Biology Teacher

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