Cypraeidae – the Cowries

Probably the most popular seashells are those in the family Cypraeidae, commonly called the cowries. The shells have highly glossy surfaces and often intricate colors and patterns. But the animal, which most people never see, can be just as interesting. In all the seashells, the shell is made by a portion of the soft mollusk body called the mantle. In most snails the mantle just lays down the shell material around the aperture of the shell as the snail shell grows. In cowries, however, the mantle forms a thin layer of tissue that completely covers the shell much of the time. Cowry mantles are often brightly colored themselves, and are ornamented with projections called papillae that vary in structure between species. The reason cowry shells retain their shine throughout their lives is that the mantle continues to lay down shell material over the entire surface and prevents other encrusting organisms from settling and growing on the shell.

There are currently 62 species of cowries known from Kwajalein. The validity of some of the species is controversial, and others could include more than one species hiding behind similar shells. It is not our intent to argue the validity of the various species, but simply to illustrate the living animals and provide some information on where and how they live here in the Marshall Islands.

A few years ago, we would have listed all these species in the genus Cypraea. However, over the past few years, research into the animals' anatomy and biochemistry (DNA) have substantiated what many people have long suspected from shell morphology alone: that there are natural groupings of species that are more closely related to each other than to other groups of cowries. Mauritia arabica and its close relatives in the genus Mauritia, for example, are certainly more closely related to each other than any of them are to any of the chick peas in the genus Pustularia. Where exactly one draws the line to say that "this much difference" is worth being placed into a different genus is somewhat subjective. We feel the groupings we have used here, mostly following Lorenz & Hubert's (2000) breakdown modified by Meyer's (2003) DNA analysis, are reasonable.

Cowries are mostly reef dwellers with many species living under rocks or in ledges and caves. A few species also live in clumps of a calcareous green Halimeda algae that sometimes thickly covers some sandy lagoon flats and slopes. Various species are known to eat either algae or sponges, possibly both. Most are more active at night, and try to hide in the dark during the day. Some are not fond of exposing any part of their animal during the day, so a fair number of these photos were taken on night dives.

The species from Kwaj are listed on the links below. The first links to a list of the Kwaj cowry species, while the second links to a page containing the same cowry names but including thumbnail images of the species where available. The species names in both lists link to pages containing pictures of most of those species. The names are ordered by the scientific Latin names; many species have common names, but since common names can and often do vary from place to place, it is always better to learn the Latin. Scientific genus and species names are supposed to be italicized, and only the genus begins with a capital letter. Even when a species is named after a person, the specific part of the name is always lower case. One or more species make up a genus, and a number of genera (plural for genus) make up the cowry family Cypraeidae. Note that the family name is not italicized.

Go to the list of Kwaj Cypraeidae.
Go to the list of Kwaj Cypraeidae with thumbnail images (slower loading).

Should anyone be interested, there are also pages for some Hawaiian cowries, as well as for a few species we have seen from a variety of other places.

There are many useful references for identifying members of Cypraeidae. Some of the ones we use nowadays include:

Burgess, C.M. 1985. Cowries of the World. Seacomber Publications, Cape Town, South Africa. 289pp.

Lorenz, F. 2002. New Worldwide Cowries. Conchbooks, Hackenheim, Germany. 292pp.

Lorenz, F. & A. Hubert. 2000. A Guide to Worldwide Cowries, 2nd edition. Conchbooks, Hackenheim, Germany. 584pp.

Meyer, C.P. 2003. Molecular systematics of cowries (Gastropoda: Cypraeidae) and diversification patterns in the tropics. Biol. Journ. Linn. Soc. 79:401-459. [Not used for identification, but contains good evidence for the breakdown of species and genera]

Poppe, Guido T. Philippine Marine Mollusks, vol. 1. Conchbooks. Hackenheim, Germany. 758pp.

Springsteen, F.J. & F.M. Leobrera. 1986. Shells of the Philippines. Carfel Shell Museum, Manila, Philippines. 377pp. [Good general shell book that includes many of the Kwaj Cypraeidae, among other shells]

Updated 25 July 2010