Cypraeidae

Lore & Background

Cowry shells are extremely rounded and egg-like, not resembling typical gastropod shells. Their glossy, polished surfaces display a variety of colors and patterns, which, combined with minor variations in shell form, have led some conchologists to recognize 60 genera and hundreds of species and subspecies. The upper surface is typically convex, while the ventral side is flattened; in fully adult shells, no spire is visible. The long, narrow aperture runs along the length of the ventral side and is lined with teeth. Juvenile cowry shells differ markedly from adults, more closely resembling the shells of some bubble snails and seldom exhibiting the same color patterns, making them hard to identify to species. Cowries have no operculum.

Reader's Guide

The Cypraeidae constitute one of the most widely distributed groups of gastropods in tropical and subtropical seas, and are among the most abundant and diversified shell groups on reefs, rocky intertidal flats, and sandy substrates in island areas. Their narrow toothed aperture makes adult shells difficult for many predators to reach into, yet they remain vulnerable: some tropical crustaceans can break the shell's dorsum; mollusc-eating cones like Conus textile can inject venom and extend their stomach into the shell to ingest the flesh; and some octopuses can gouge a small hole using a special barb and acidic secretion to inject venom. The eating habits of cowries are poorly known, as most species are nocturnal and cryptic, but sponges are the most commonly described prey. Off the coasts of Australia, common species eat sponges, and on Caribbean coral reefs they are known to eat sponges that are otherwise chemically defended against other predators. For nearly 200 years, every species was placed in one genus, Cypraea, but in 2002 the cowries were divided into many different genera.

Did You Know?

• Cowry shells are extremely smooth and shiny because in the living animal the shell is nearly always fully covered by the mantle.
• Juvenile cowry shells do not resemble adult shells and are hard to identify to species.
• Some octopuses can gouge a small hole through a cowry shell using a special barb and acidic secretion to inject venom.
• For nearly 200 years, all cowry species were placed in the single genus Cypraea, but were divided into many genera in 2002.