Those aren’t eyes of the front of this Barreleye Fish‘s head. Those are olfactory organs called nares. The eyes are those two large green orb-ish things inside of its transparent head. It’s about 6 inches long and was discovered around 2,000 feet deep off of the coast of central California by the Monterey Bay Aquarium Research Institute (MBARI).
The green lens atop each of the fish’s eyes filters out what little sunlight makes it down from the surface, allowing the fish to focus on the bioluminescence of small jellies or other prey passing overhead. Then the eyes rotate forward to follow the prey, allowing the fish to home in on its meal.
It took from 1939 to 2004 before scientists were able to find a living example of this fish…. 65 years! From MBARI:
MBARI researchers Bruce Robison and Kim Reisenbichler used video taken by unmanned, undersea robots called remotely operated vehicles (ROVs) to study barreleye fish in the deep waters just offshore of Central California. At depths of 600 to 800 meters (2,000 to 2,600 feet) below the surface, the ROV cameras typically showed these fish hanging motionless in the water, their eyes glowing a vivid green in the ROV’s bright lights. The ROV video also revealed a previously undescribed feature of these fish–its eyes are surrounded by a transparent, fluid-filled shield that covers the top of the fish’s head.