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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, although DNA analysis such as that of Meyer (2003) provides data to back up the generic breakdown. We feel the groupings we have used here, mostly following Lorenz (2017), 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 link at the top of the page and just below this paragraph. It links to a page containing thumbnail images of the species. The species names and thumbnails 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.
The cowries have attracted considerable interest from taxonomists and collectors, and this had led to many of the species being further broken into subspecies, different variations of the species usually from different areas. Subspecies can usually be differentiated by characters of the shell, suggesting that different subspecies are isolated from one another and are diverging. Given enough time, many would likely diverge enough to become separate species. We do not indicate the subspecies in the listing or page titles, but we try to indicate in the text on each page which subspecies is found in the Marshalls.
Go to the menu of Kwaj Cypraeidae
Should anyone be interested, there are also pages for cowries from our travels, including the Hawaiian Islands, Bali, Anilao, and Solomon Islands, plus a few from Pohnpei, the Sea of Cortez and central California.
There are many useful references for identifying members of Cypraeidae. Some of the ones we use nowadays include (hover mouse over reference link to see complete reference):