"Bathylychnops exilis—a Fish With Six Eyes
"Discovered in 1958, inhabiting depths of 300-3000 ft within the northeastern Pacific Ocean, and belonging to the spookfish (opisthoproctid) family, Bathylychnops exilis is a slender, 18-in-long, pike-like species with noticeably large eyes. These provide efficient prey de tection in the dim light of its deep undersea world, but that is not all. Housed within the lower half of each eye is a second, smaller eye, pointing downwards and termed the secondary globe, which comes complete with its own retina and lens. This extraordinary arrangement prob ably increases the species’ sensitivity to light within its shadowy surroundings. Yet, as if its possession of four eyes were not sufficiently strange, behind each of the two secondary globes is a third, even tinier eye-like organ, though these do not have retinas, serving instead merely to direct incoming light into the fish’s large, principal eyes. Intriguingly, its pair of secondary globes were once thought to be light-producing organs—hence its name, Bathylychnops (‘deep lamp-eye’). In popular parlance, it is called the six-eyed or javelin spookfish."
