Discovered in the deep: the incredible fish with a transparent head

The barreleye fish has extremely light-sensitive eyes that can rotate within a transparent, fluid-filled shield on its head. The two spots above its mouth are similar to human nostrils. Picture: Monterey Bay Aquarium Research Institute

In the ocean’s shadowy twilight zone, between 600 and 800m beneath the surface, there are fish that gaze upwards through their transparent heads with eyes like mesmerising emerald orbs. 

These domes are huge spherical lenses that sit on a pair of long, silvery eye tubes — hence its common name, the barreleye fish (Macropinna microstoma).