But now, incredibly, new research suggests that the cleaner wrasse—a tiny, tropical reef fish—can recognize itself too, making it the first fish to do so. Scientists have long used a mirror ...

The bluestreak cleaner wrasse is just one of about 600 different species of wrasse. It's a little thing, about 3.9 inches (10 cm) long on average, with, well ... a blue streak down its side.