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Frogs
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< Green
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Frog >
Frog >
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"Blue" Green Frog
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"Frogs are not green because they have green pigment in their skin. Instead, they use a complex arrangement of cells, a more complicated approach to be sure, but one that provides a tremendous potential for changing and adjusting their hue. In their skins they have three types of pigment cells (called chromatophores) stacked on top of each other. At the bottom are melanophores, containing a mostly dark pigment called melanin. These are the same cells that can make human skin various shades of brown. On top of the melanophores are iridophores, packed with highly reflective bundles of purine crystals, and on top of the iridophores are xanthophores, usually packed with yellowish pteridine pigments. In the typical green frog, light penetrates to the iridophores, which act like tiny mirrors to reflect mostly blue light back into the xanthophores above them. These cells act like yellow filters, so the light escaping the skin surface appears green to our eyes. Occasionally a frog is found that lacks the yellow xanthophore cells, and these are hard to miss because they are bright blue!" |
