Cowries have long played a role in human history, as jewelry, currency, and symbols of stature within a village or tribe. Their highly polished and rounded shells are what immediately attract most people to them, but few can tell you what the animal that once inhabited the shell looks like. The cowry and cowry allies belong to a superfamily of marine gastropods whose shells are rounded, concealing the spire that is usually visible on the outside of gastropod shells. The bottom of the shell is flat, and features a thin aperture, or slit, through which the mantle protrudes and completely engulfs the outer shell. This action of the living cowry is what’s responsible for the polished exterior; the secretions from the mantle build the shell continuously from the outside in while protecting it from abrasions and grime. The mantle will typically be covered in papillae, which provide camouflage as well as respiration for the animal as it grazes along the reef on algae, sponges, and coral. The mantle of some cowry species will even take on the color of whatever they’re feeding on, adding to the power of their camouflage on the reef. A shell that appears discarded may in fact still be housing a living gastropod, so be sure to leave them where you see them!
Have you ever seen a live cowry on the reef?
Top image via Chika