The fascinating aspect of the barreleye fish is the tubular eyes which are excellent at collecting light at depths up to 2500m. The puzzling part is that the eyes appear to be fixed in place directly above its head. This had baffled physiologists for decades because it would be almost impossible for the fish to look for food. Recently scientists using a remotely operated vehicle studied the fish at depths ranging from 600-800 meters. They discovered a previously unknown fact, the tubular eyes exist behind a transparent fluid filled dome and the eyes can rotate within a transparent shield that covers the fish’s head. This allows the fish to peer up at potential prey or focus forward to see what it is eating. The Barreleye Fish was first discovered in 1939 but the transparent nature of the fish wasn’t known because when the fish was caught in nets at a different depth of water the see through part is destroyed.
Interesting Fact: Keep in mind when you look at the above picture that the two small holes in front of the fish are not eyes. The eyes are the two green domes inside the top of the head.