Ponderous Dosinia Clam Shell, Dosinia ponderosa
Ponderous Dosinia Clam Shell, Dosinia ponderosa. Shell collected within the intercoastal water off Puerto Adolfo Lopez Mateos, Baja California Sur, March 2018. Size: 10.0 cm (3.9 inches) x 9.5 cm (3.7 inches).
Ponderous Dosinia Clam Shell, Dosinia ponderosa. Shell collected off the beach at Punta Chivato, Baja California Sur, February 2022. Size: 11.6 cm (4.6 inches) x 11.2 cm (4.4 inches). Collections, photographs and Identifications courtesy of Colin Campbell, DVM, Punta Chivato, Baja California Sur.
Phylogeny: The Ponderous Dosinia Clam Shell, Dosinia ponderosa (Gray, 1838), is a bivalve mollusk that is a member of the Veneridae Family of Venus Clam Shells. The genus Dosinia is one of one hundred seven genera within this family, and there are one hundred one species in this genus. They are also known as the Heavy Dosinia Clam Shell, the White Clam Shell, and the Disk Dosinia Shell and in Mexico as Almeja Mantequilla and Dosinia Redonda.
Description: Ponderous Dosinia Clam Shells have a large thick shell that is equivalve (both values are equal in size and shape) and subcircular in outline. Both valves are only slightly convex, giving the shell a flattened, disk-like look. The hinge plate is broad and strong. The exterior of the shell is marked with low concentric ridges, which become smoother as the shell matures. The exterior of the shell is white in color but is usually covered by a yellow periostracum, giving rise to its Spanish name Almeja Mantequilla or “Butter Clam.” The interior is white. Ponderous Dosinia Clam Shells reach 14.7 cm (5.8 inches) in length and and 14.2 cm (5.6 inches) in height.
Habitat and Distribution: Ponderous Dosinia Clams reside in shallow burrows within sand and mud substrates. They live intertidally, and at depths up to 60 m (200 feet). They are a subtropical to tropical Eastern Pacific species that are found in all Mexican waters of the Pacific Ocean with the exception that they are absent from north of Scammon’s Lagoon, Baja California, along the central and northwest coasts of the Baja Peninsula.
Ecology and Behavior: Ponderous Dosinia Clams are suspension feeders that feed primarily on microalgae. They are gonochoric and reproduce sexually, through broadcast spawning. Their engagement in any type of commensal, parasitic or symbiotic relationship has not been formally documented. 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: Artemis ponderosa, Arthemis ponderosa, Cytherea gigantea, Dosinia (Dosinia) grandis, Dosinia (Dosinidia) ponderosa, Dosinia (Dosinidia) titan, Dosinia grandis, Dosinia titan, and Venus cycloides.