Giant Eyes

Cystisoma (a type of hyperiid crustacean) has one huge pair of eyes. You can see the eye pictured here as the entire surface of its head and the convex orange sheet of retinal cells in the top left of the photo. Its eyes look almost exclusively upwards, possibly to watch out for animals overhead. Cystisoma is completely transparent—even its gut (the bubble-like blue outline you can see in the picture) is see-through. This transparency keeps it from being seen by predators in the open ocean, where there is no place to hide. Cystisoma can reach lengths of about the size of a human hand (7 inches or 18 cm). See more images of mid-water creatures in our slideshow.