Frog skin not only comes in a beautiful variety of shapes, colors and patterns, there is purpose to it and a complexity that creates it. Frog skin has several layers to it, starting with the outermost, the epidermis. This layer is for protection. It contains many keratinized cells, (we mentioned keratin in the Legs section, but it is a hardy waterproof protein essentially), and glands, and does not really have much or any color to it. The following layers have chromatophores, which are the pigments that give skin its color. When skin cells are stretched out or pulled in they either expose their pigments or cover them up changing the color shade. There are a couple of situations that can cause this to happen automatically—temperature and stress—but the frog can also control these changes whenever it wants. It’s all thanks to the nervous system really, which connects the brain to the chromatophores. The second layer of skin controls the shade by containing black pigments called melanophores. Below that are layers that contain other pigments and an interference layer. The other pigments could be yellows, reds, oranges, or iridescent. But where are the greens and blues? That’s where the interference layer comes in. It contains polygonal cells, (polygonal is a closed shape with many sides), which may or may not also contain pigments. If these cells have some yellow pigments the skin looks green to us, if it does not have any pigments the skin looks blue to us. And just because the interference layer may be empty in one section of the skin it may contain yellow or some other color pigments on another part of the body, giving the skin a pattern. And, you know, just because frogs have great colors doesn’t mean there aren’t the occasional quarks every now and then. Sometimes a frog may be born and become an adult but have no melanophores in the skin or eyes. Instead they look white, cream, or yellow. When this happens the frog is an albino. This doesn’t mean the frog is a quark, no, just that there is a quark somewhere in the frogs genes that didn’t allow the skin cells to produce any melanophores.
Works Cited:
Behler, J. L., & Behler, D. A. (2005). Frogs: A chorus of colors. New York, NY: Sterling Publishing Co., Inc.
Beltz, E. (2005). Frogs: inside their remarkable world. Buffalo, NY: Firefly Books Ltd.
Mongabay.com
Rhett A. Butler - San Francisco, CA.
1999-2008.
Photo taken by Ellen Pitre
Frogs
February 13, 2009