Washington Clam Shell, Saxidomus nuttalli

Washington Clam Shell, Saxidomus nuttalli. Shell collected off the beach in the greater San Diego area, San Diego, California, March 2018. Size: 12.4 cm (4.9 inches) x 8.8 cm (3.5 inches). Collection, photograph and identification courtesy of Bob Hillis, Ivins, Utah.

Phylogeny: The Washington Clam Shell, Saxidomus nuttalli (Conrad, 1837), is a bivalve mollusk that is a member of the Veneridae Family of Venus Clam Shells. The genus Saxidomus is one of one hundred seven genera in this family, and there are three species in this genus.  They are also known as the California Butter Clam Shell.

Description: The Washington Clam Shell is sturdy with an oval profile. They have a moderately inflated profile, and prominent beaks. The exterior of the shell is sculpted with fine, but sharply defined, concentric ridges. The exterior is light gray to brown color, often with a rusty wash. The interior is white, sometimes with a purple blush. These shells have a brown periostracum. Washington Clam Shells reach a maximum of 15.6 cm (6.1 inches) in length and 11.1 (4.4 inches) in height.

Habitat and Distribution: Washington Clams are found buried in sand and mud substrates, usually in protected waters, intertidally, and at depths up to 10 m (35 feet). They are a subtropical Eastern Pacific species  that are found in Mexican waters of the Pacific Ocean on a limited basis being found north of Punta Rompiente, Baja California Sur, along the central and northwest coasts of the Baja Peninsula.

Ecology and Behavior: Washington Clams are suspension feeders that feed primarily on plankton and suspended organic matter. In  turn they are preyed upon by shorebirds, gastropods, and sea stars. 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 the Washington Clams has not been formally evaluated. However, they are fairly common with a relatively wide distribution and should be considered to be of Least Concern. They are edible and are harvested commercially, recreationally, and by artisan fisheries. They have been an important food source to indigenous people for thousands of years.

Synonyms: Saxidomus arata, Saxidomus aratus, Saxidomus nuttalli latus, Saxidomus squalidus, and Tapes gracilis.