Pearl Oyster Shells of the Margaritidae Family
One Pearl Oyster Shell of the Margaritidae Family can be found in this website:
Panama Pearl Oyster Shell, Pinctada mazatlanica. A representative of the Margaritidae Family of Pearl Oysters.
Phylogeny: Pearl Oysters of the Margaritidae Family (Blainville, 1824) are bivalve mollusks in the order Ostreida. There are three superfamilies in this order: Ostreoidea, Pinnoidea, and Pterioidea. Until fairly recently the superfamily Pterioidea was divided into three families. That superfamily have now been divided into six families. The Family Margaritidae was split from the Pteriidae Family. The most visible distinction between these two families is the width of the hinge plate. The genus Pinctada is the only genus in the Margaritidae Family, and there are twenty-one species in that genus. This family was first described in 1824 by the French naturalist Henri-Marie Blainville. This is important because there is a second valid Margaritidae Family, consisting of gastropod snails. This Family was described in 1924 by German zoologist Karl Theile. The names and the dates become essential to separate these two families.
Description: Pearl Oysters of Family Margaritidae (Blainville, 1824) are quadrate or circular in outline and flattened in profile. They are inequivalve, with the left valve being larger and more inflated than the right. They are permanently attached to the substrate by their left valve. These shells are thin and fragile. They have a single adductor muscle, which leaves a reniform (kidney-shaped) muscle scar inside the shell. They have a long straight hinge which lacks teeth. The auricles (ears) are reduced, unlike the posterior wing of Pteriidae Pearl Oysters. Their exteriors vary from smooth to strongly rugose with foliaceous laminae. Their interiors are nacreous. Species in this family produce high quality pearls. Shells in this Family are medium to large in size, with the largest species being 30 cm (12 inches) in width. There can be considerable variation in shape, color, and sculpture within a species in this family. In areas where more than one species is found identification can be difficult and sometimes requires several specimens.
Habitat and Distribution: Margaritidae Pearl Oysters are found primarily in warmer, protected, waters. They live intertidally, attached to rocks and mangrove roots, as well as in deeper water attached to gorgonians and black coral branches. Some species are found as deep as 75 m (246 feet). They attach to the substrate with filamentous byssus. Margaritidae Pearl Oysters are found worldwide in subtropical and tropical seas. Three species from this family are found in Mexican waters.
Natural History: Margaritidae Pearl Oysters are suspension feeders, filtering plankton and fine detritus from the surrounding water. In turn they are preyed upon by crabs, predatory mollusks and sea stars. They are protandric hermaphrodites that reproduce sexually through broadcast spawning, with external fertilization. These shells have been harvested extensively for their pearls and their nacreous shells, which were historically used for making buttons.