California Jackknife Clam, Tagelus californianus

California Jackknife Clam, Tagelus californianus. Shell collected from within the estuary of the Magdalena Bay complex, Baja California Sur, October 2018. Size: 8.2 cm (3.2 inches) x 2.2 cm (0.9 inches). Identification courtesy of Bob Hillis, Ivins, Utah.

Phylogeny: The California Jackknife Clam, Tagelus californianus (Conrad, 1837), is a bivalve mollusk that is a member of the Solecurtidae Family of Short Razor Clams. The genus Tagelus is one of four genera in this family, and there are eleven species in this genus. They are also known as the California Tagelus and in Mexico as Almeja Navaja and Tagelo Californiano.

Description: The California Jackknife Clam shell is thin, and has a very elongate oval profile, with a central beak and bluntly rounded ends. The exterior is sculpted with very fine concentric lines. The shell has a thick yellowish to dark brown periostracum that is usually worn away except around the ends and margins. The interior and exterior are  a uniform dull white color. The California Jackknife Clam  reaches  a maximum of 13 cm (5.1 inches) in length and 3.5 cm (1.4 inches) in height.

Habitat and Distribution: California Jackknife Clams live buried in sandy mud within protected bays or estuaries. Their burrows are permanent and may be up to 50 cm (20 inches) in depth. The shell can move quickly up and down in its burrow. They are found in intertidally and subtidally,  and rarely in water that is greater than 3 m (10 feet) in depth. California Jackknife Clams are a temperate and tropical Eastern Pacific species. In Mexican waters they are found along the entire west coast, including the entire Gulf of California.

Ecology and Behavior:  California Jackknife Clams are suspension feeders that feed primarily on plankton and suspended organic matter. They are prey for fish, crabs, mollusks, and shore birds.  They are gonochoric and reproduce sexually, through broadcast spawning, with external fertilization. They reproduce from April through August.  There is no mention in the available literature of them engaging in any types of parasitic, commensal, or symbiotic relationships. California Jackknife Clams are sold commercially and sold for human consumption and fishing bait. 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: Solecurtis (Cultellus) californianus, Solecurtis californianus, Solecurtis violascens, and Tagelus violascens.