Palmate Oyster Shell, Saccostrea palmula
Palmate Oyster Shell, Saccostrea palmula. Shell collected in the greater Los Cabos area, Baja California Sur, March 2016. Size: 7.5 cm (3.0 inches) x 5.5 cm (2.2 inches).
Phylogeny: The Palmate Oyster, Saccostrea palmula (Carpenter, 1857), is a bivalve mollusk that is a member of the Ostreidae Family of True Oyster Shells. The genus Saccostrea is one of sixteen genera in this family, and there are twelve species in this genus. They are known in Mexico as Ostra Palmeada. The word palmula is Latin for the palm of a small hand, referring to the appearance of this shell’s interior.
Description: The Palmate Oyster shell has an irregular ovate outline, often with scalloped margins. The left valve is deeper than the right valve. The right valve may be concave, flat, or slightly convex, and it fits within the left valve. The exterior of the shell is rough in texture. They are gray to brown in color, sometimes with a purplish or greenish tinge or rays. The interior is white, sometimes with greenish or purple blotches. The interior margin may be purple. The interior has a noticeable muscle scar. Palmate Oyster Shells reach a maximum length of 7.5 cm (3.0 inches) x 5.5 cm (2.2 inches).
Habitat and Distribution: Palmate Oysters are found attached to mangroves, rocks and other hard surfaces. They reside in the intertidal zone at depths up to 3 m (10 feet). They are a subtropical to tropical Eastern Pacific species that are found in Mexican waters of the Pacific Ocean from the San Ignacio Lagoon, Baja California Sur south to Guatemala. They are found throughout the Sea of Cortez.
Ecology and Behavior: Palmate Oysters are suspension feeders that feed primarily on planktonic algae and suspended organic matter. They are gonochoric and reproduce sexually, through broadcast spawning, with external fertilization. They are known to host the parasitic pea crab Austinotheres angelicus, which steals food from its host and can damage the host’s gills. They also host the parasitic protozoan Perkinsus marinus, which causes Dermo disease. There is no mention in the available literature of them engaging in any types of commensal or symbiotic relationships. From a conservation perspective they have not been formally evaluated however they are fairly common with a relatively wide distribution and should be considered to be of Least Concern.
Synonyms: Dendostrea amara, Ostrea amara, Ostraea mexicana, Ostrea Conchaphila var. palmula, Ostrea dalli, Ostrea frons, Ostrea tubulifora, and Saccostrea tubulifora.