Spookfish Uses Mirrors for Eyes

Mirrors give fish diverticular eyes

Spookfish
Dr. Tammy Frank, Habor Branch Oceanographic Institution

Odd looking? That's an understatement. But the barrelye, better known as the spookfish, just got its claim to fame. What makes this skinny, sea creature so special? Just look into its eyes. Literally. The spookfish is the first vertebrate discovered to use mirrors for eyes. Instead of using lenses to focus light and create images, the spookfish utilizes reflective mirrors.

At first glance, the fish looks to have four eyes (spooky, right?), but Professor Julian Partridge from the University of Bristol confirms the spookfish has only two. According to Partridge, "In nearly 500 million years of vertebrate evolution, and many thousands of vertebrate species living and dead, this is the only one known to have solved the fundamental optical problem faced by all eyes – how to make an image – using a mirror."

The spookfish has "diverticular" eyes which are split into two connected parts. One part of the eye looks upward into the waters above while the other, resembling a dot on the side of the fish's head, points downward to the sea below. This setup gives the spookfish an advantage in deep waters, allowing the fish to see food above and at the same time, potential threats below.

Last year, scientists from Tuebingen University in Germany caught a spookfish off the coast of Tonga, an island in the Pacific. The spookfish was discovered 120 years ago, but until recently, a specimen had never been caught.
Now who's the cool cat...err…fish in town?