Lesson 1
Cells full of tiny mirrors
Iridophores (say "ih-RID-oh-fors") are color cells in the skin of many fish, frogs, and lizards like chameleons. Squids and octopuses have them too.
Most color cells hold pigment, a colored chemical, like paint. Iridophores are different. They are packed with stacks of flat, see-through crystals. In many fish and lizards, the crystals are made of a chemical called guanine.
Wow!Guanine is also one of the four "letters" in DNA. These animals use it to make tiny mirrors!
Lesson 2
Shine, shimmer, and change
When light hits the stacks of crystals, some colors bounce back and others pass through. That makes shiny colors without any paint.
- The silver shine on the sides of many fish comes from iridophores.
- Blue and green shimmer on some frogs and lizards often comes from iridophores too.
- Scientists found that some chameleons change color partly by changing the space between their crystals.
Shiny colors like these can help an animal hide, show off, or send a message.
Try thisBlow a soap bubble and look at its swirly colors. That shimmer comes from light bouncing off thin layers, the same kind of trick iridophores use. Then press Shine light on the 3D model.