Here we look into the face of the thorny oyster (Spondylus Americanus). Unlike most shallow-water oyster species, the Atlantic thorny oyster is a solitary creature that lives permanently cemented to the deeper coral reef.
Though there are many species of Spondylus, they vary considerably in appearance and range. They are grouped in the same superfamily as the scallops, however like the true oysters they cement themselves to rocks, as opposed to attaching themselves by a byssus (a silk like fabric that molluscs attach themselves to the rock work with). The two parts of their shells are hinged together with a ball and socket kind of hinge, rather than a toothed hinge as is more common in other bivalves.
Spondylus have multiple eyes around the edges of the shell, and they have a fairly well developed nervous system. Their nervous ganglia are concentrated in the visceral region, with recognisable optic lobes, connected to the eyes.
Images are produced by concave mirrors located behind the retina, directly in front of which is the lens used for optical correction of the highly distorted mirror images..
The mirror are constructed like reflected glass panels, with 30 layers of fine guanine crystals closely stacked between double membranes.
Other creatures including the deep-water crab Gigantocypris, lobster and crayfish also carry mirror eyes.