Six Eyed Spookfish (Bathylychnops exilis)
This species of deep sea fish possesses a large pair of principal eyes and a second, smaller pair (known as secondary globes) positioned within the lower half of its principle eyes, each possessing its own lens and retina. The secondary globes are thought to facilitate with light detection in the pitch black world. A third set of ‘eyes’ (having no retina) are located behind the secondary globes and serve to direct light into the fish’s primary eyes.
Image 1: Hans-Joachim Wagner ; Image 2 Tammy Frank, Habor Branch Oceanographic Institution