I spy with my barreleye, a new Fresh from the Deep! During a dive with our education and outreach partner, the Monterey Bay Aquarium, the team came across a rare treat: a barreleye fish (Macropinna microstoma).
The ROV Doc Ricketts was launched between 600 and 800 meters (2,000 to 2,600 feet) deep into the bay when it came across a dark-bodied fish with glowing tubular eyes that faced upwards inside a transparent head. The position of the eyes begged the researchers to ask how the fish eats. They soon learn that these unique peepers are movable underneath their vast lids.
MBARI researchers learned the barreleye can rotate its eyes beneath that dome of transparent tissue. …They were able to bring a net-caught barreleye to the surface alive, where it survived for several hours in a ship-board aquarium. Within this controlled environment, the researchers were able to confirm what they had seen in the ROV video–the fish rotated its tubular eyes as it turned its body from a horizontal to a vertical position.
They also discovered how this odd look fish hunts for food.
Most of the time, the fish hangs motionless in the water, with its body in a horizontal position and its eyes looking upward. The green pigments in its eyes may filter out sunlight coming directly from the sea surface, helping the barreleye spot the bioluminescent glow of jellies or other animals directly overhead. When it spots prey (such as a drifting jelly), the fish rotates its eyes forward and swims upward, in feeding mode.