By Wendy Langhans
If you somehow acquired x-ray vision and could see through my mud-caked hiking boots, you’d find ten toenails gleaming with vivid red nail polish, a leftover from a wedding we recently attended.
I can’t remember the exact name of the color - I think it was something like “Crimson... Cardinal... Vermilian... Carmine... Red.”
But did you know that the chemical that gave my nail polish a lustrous finish is the same chemical that gives fish a shiny metallic sheen? What’s that chemical, you ask? (Here’s a hint - it’s one of the four chemical bases found in DNA.)
Iridescent nail polish
It’s guanine, or in the case of fish, guanine crystals.
Recent studies  have found that the skin of certain fish contain highly iridescent photonic crystals made of guanine. What’s more, these crystals are deliberately shaped to maximize reflection.
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Guanine crystals grown in a laboratory are prism-shaped, while fish crystals resemble a stack of thin plates .
Now why would reflective skin be useful to fish? To hide from predators, of course. Anyone spending time near a lake knows just how reflective the water’s surface can be.
Water can be highly reflective
And there are plenty of fish-eating birds hanging around, such as cormorants and herons.
Cormorants are fish eaters
So are Black-Crowned Night-Herons
The cosmetic industry uses “fish scale essence ” to achieve a lustrous, pearl-like gloss. "Pearl" or "guanine" is literally made from small fish scales and skin, suitably cleaned, and mixed with solvents such as castor oil and butyl acetate. Fish scale essence has also been used to make faux pearls  for decorating clothing, which you can see in an upcoming exhibit at Los Angeles County Museum of Art.
How ironic that fish use guanine to help hide, while we humans use it to make ourselves more attractive. And what’s even more ironic, the name guanine comes from the word “guano” (bird scat), from which the chemical guanine was first isolated and identified in 1844. Maybe that nail polish is suitable for wearing with hiking boots, after all.
Upcoming Outdoor Events:
Every Saturday at 1:00 PM. Animal Show at Placerita Canyon.
For more information, click here .
Friday, June 25, 9-11 PM. Almost Full Moon Hike. Towsley Canyon. Night is a special time to explore the park. For map, click here .
Trail Maintenance Schedule. Come join our volunteers as they help maintain our trails. Contact Steve at firstname.lastname@example.org  for time and place.
Wednesday mornings, June 16, 23 & 30.
Saturday mornings, June 12 & 26
You can listen to stories like this every Friday morning at 7:10 a.m. on "The Hike Report", brought to you by your hometown radio station KHTS (AM1220) and by the Mountains Recreation and Conservation Authority.