Without a mirror, it can be hard to tell if you're blushing, or have spinach in your teeth. But one color-changing fish has evolved a clever way to keep watch on the parts of itself that lie outside ...

Hogfish can change their color in less than a second to blend in with their surroundings. Reinhard Dirscherl \ ullstein bild via Getty Images Like a chameleon, a hogfish can quickly change the color ...