Tagincredible fish

In the ocean’s shadowy twilight zone, between 600 and 800 metres 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). The green tint (which actually comes from a yellow...