Why So Blue?

People like the color blue. In fact, it has consistently been ranked as the world’s favorite color. But besides the sky or water, blue is a hard color to come by in nature, especially when it comes to the animal kingdom.

This blog post by the Mother Nature Network features twelve blue creatures. We hope you enjoy them as much as we did (especially the sea slug known as a blue dragon). What is your favorite blue animal?


12 elusively blue animals: The rarest critters of them all

Blue animals: Iguana
Photo: Matt Reinbold/Flickr
Blue has long been considered the world’s most popular favorite color, even though it’s the rarest occurring pigment found in nature. Sure, we can see blue quite easily in the sky and water, but its tendency to appear in animals, like the endangered Grand Cayman blue iguana above, is fairly uncommon.
The main reason why blue is so elusive has to do with the relatively narrow range of pigments that cause coloration in animals. Red and orange pigments are produced by carotenoids, brown and black pigments are produced by eumelanins and yellow pigments are produced by pteridine compounds.
While plants can produce blue pigments thanks to anthocyanins, most creatures in the animal kingdom are unable to make blue pigments. Any instances of blue coloration you come across in animals are typically the result of structural effects, such as iridescence and selective reflection.
Take, for example, the bluejay. This little bird produces melanin, meaning it should technically appear almost black. However, tiny air sacs in the bird’s feathers scatter light, making it appear blue to our eyes. This is called Rayleigh scattering, a phenomenon that is also responsible for the age-old “why is the sky blue?” question.
Even though these critters are rare, they do, in fact, exist. Here’s a look at just a few animals with exquisite blue coloring:
Blue animals: Little Blue Heron
Little blue heron
* * *
Blue animals: Blue-ringed octopus
Photo: Angell Williams/Flickr
Blue-ringed octopus
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Blue animals: Blue-eyed kitten
Blue-eyed kitten
* * *
Blue animals: Bluejay
Photo: Randen Pederson/Flickr
* * *
Blue animals: Metallic blue bee
Augochloropsis sumptuosa, also known as the sweat bee
* * *
Blue animals: Moon jellies
Photo: Johnathan Nightingale/Flickr
Moon jellyfish
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Blue animals: Frog
Photo: Philipp Weimer/500px
Blue poison dart frog
* * *
Blue animals: Glaucus atlanticus
Photo: Imtorn/Wikimedia
Glaucus atlanticus, also known as a blue dragon
* * *
Blue animals: Morpho butterfly
Photo: William Warby/Flickr
Blue morpho butterfly
* * *
Blue animals: Arizona bark scorpions under black light
Photo: Matt Reinbold/Getty Images
Arizona bark scorpions, as seen under a black light
* * *
Blue animals: Peacock
Photo: Soren Kleen/500px

Read more: http://www.mnn.com/earth-matters/animals/blogs/12-elusively-blue-animals-the-rarest-critters-of-them-all#ixzz33VX3FrMB

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