The Barreleye Fish’s Amazing Transparent Head

Aptly known as the spook fish, this translucent ocean dweller’s telescope-like eyes face directly upward to keep an eye on potential prey. To enhance its vision, the barreleye’s head is completely transparent, so as to allow its eyes to collect even more incident light and aid in its collection of food. Pretty cool!

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.