Natures wonders: Chameleon color change (Introduction)

by David Turell @, Wednesday, March 11, 2015, 14:04 (1624 days ago) @ David Turell

Shifting onboard crystals size and color reflections:

"Chameleon colors aren't just for camouflage. When panther chameleons (Furcifer pardalis) in Madagascar fight over territory, a dazzling display precedes their contests: resting males, typically green and inconspicuous, turn yellow or orange; red patches on their bodies can brighten, and blues can fade to whitish tints. The color changes, which are completely reversible and occur within minutes, are not the result of shifts in pigments alone. Results published today (March 10) in Nature Communications suggest they are the result of quick changes to light-reflecting guanine nanocrystals, which create structural color within chameleon skin.

"Two layers of cells known as iridophores contain these nanocrystals. A superficial layer, known as S-iridophores, actively alters the spacing of these crystals to cause the rapid color changes, while a deeper layer, made up of D-iridophores, reflects a broader spectrum of light near the infrared wavelengths. In addition to camouflage and flashy fights, these cells may play a key part in keeping these lizards cool.

"'The surprising result here is that these animals can actually actively tune the geometry of these crystals in their iridophores, and they can do that reversibly,” Milinkovitch told The Scientist. “They can choose to go from green to yellow and back to green within minutes.”

"Unlike S-iridophores, which are fully developed only in adult males, D-iridophores are common across the species and in other distantly related chameleons. Guanine crystals within the more deeply embedded D-iridophores are larger, more disorganized, and did not appear to rearrange to contribute to color changes. Instead, they reflected approximately 45 percent of radiation in the infrared wavelengths, suggesting the layer acts as a broad-band reflector to protect these animals from extreme heat.

"Although the results indicate that panther chameleons tune their color displays via crystals, precisely how they change the spacing in these crystal lattices is still unknown. The mechanisms may be hormonal, controlled by neurons, or some combination of both, according to the researchers. In future work, Milinkovitch and his colleagues aim to test whether cytoskeletal elements play a part in moving crystals around within S-iridophores."

In this complexity how did chance mutations do it?


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