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 Clam Shells. 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 Shell 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 that are found in all Mexican waters of the Pacific Ocean.

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 shorebirds. They are gonochoric and reproduce sexually, through broadcast spawning, with external fertilization. They reproduce from April through August. Their engagement in any type of commensal, parasitic, or symbiotic relationship has not been formally documented. From a conservation perspective the California Jackknife Clam has not been formally evaluated. However, they are fairly common with a relatively wide distribution and should be considered to be of Least Concern. California Jackknife Clams are sold commercially and sold for human consumption and fishing bait.

Synonyms: Solecurtis (Cultellus) californianus, Solecurtis californianus, Solecurtis violascens, and Tagelus violascens.