Panama Pearl Oyster Shell, Pinctada mazatlanica
Panama Pearl Oyster Shell, Pinctada mazatlanica. Shell collected from a tidal pool at Km 17, El Tule, Baja California Sur, February 2018. Size: 4.4 cm (1.7 inches) x 4.5 cm (1.8 inches).
Phylogeny: The Panama Pearl Oyster, Pinctada mazatlanica (Hanley, 1856), is a bivalve mollusk that is a member of the Margaritidae Family of Pearl Oyster Shells. The genus Pinctada is the only genus in this family, and there are twenty-one species in this genus. They are also known as the Black Lipped Oyster, the Calafia Pearl Oyster, and the Mazatlán Pearl Oyster and in Mexico as Madre Perla, Ostra Perifera Panamena, Ostra Perlera Vidua and La Madre Perla Calafia.
Description: The Panama Pearl Oyster shell has a disk-like appearance, being round and flattened. Both valves are similar in shape, but the lower valve has a notch for the byssus which is utilized to attach to the substrate. The hinge does not extend as wings. The external surface is scaly. The exterior of the shell is a mix of yellowish brown, and greenish gray regions, marked with darker radial rays. The interior is iridescent with a dark gray, black, or brown margin. The interior muscle scar is pronounced. Panama Pearl Oysters reach a maximum of 15 cm (5.9 inches) in length and 15 cm (5.9 inches) in height.
Habitat and Distribution: Panama Pearl Oysters are found attached to rocks, gorgonians and other hard surfaces in the intertidal zone, and to depths up to 24 m (80 feet). They are a subtropical to tropical Eastern Pacific species that are found in all Mexican waters of the Pacific Ocean with the exception of the west coast of the Baja Peninsula.
Ecology and Behavior: Panama Pearl Oysters are suspension feeders that feed primarily on planktonic algae and suspended organic matter. They are sequential hermaphrodites, beginning life as males and becoming female when they reach around 10 cm in length. They reproduce sexually, through broadcast spawning, with external fertilization. This species is known to host the pearl shrimps Pontonia margarita and Pontonia pinnae, and the Pacific Pearlfish, Carapus dubius in its mantle cavity in what appears to be a commensal relationship. They also host algae and other ectobionts. Panama Pearl Oysters produce valuable pearls and have been harvested for hundreds of years, by both indigenous peoples and Europeans. Over harvesting prompted the Mexican government to outlaw commercial harvesting in the 1940’s. Since then, farming of this species has taken over and populations have recovered. From a conservation perspective they have not been formally evaluated however they are fairly common with a relatively wide distribution and should be consider to be of Least Concern.
Synonyms: Avicula barbata and Meleagrina mazatlanica.