Rough Clam Shell, Leukoma aspirrima

Rough Clam Shell, Leukoma asperrima. Shell collected off the shore of Bahía Concepción, Baja California Sur, October 2019. Size: 2.7 cm (1.1 inches) x 2.5 cm 1.0 inch). Collection and identification courtesy of Bob Hillis, Ivins, Utah.

Phylogeny: The Rough Clam Shell, Leukoma asperrima (G.B. Sowerby I, 1835), is a bivalve mollusk that is a member of the Veneridae Family of Venus Clam Shells. The genus Leukoma is one of one hundred seven genera in this family, and there are twenty-three species in this genus. They are also known as Rough Littleneck Shells and in Mexico as Almejuela Áspera. The name asperrima comes from the Latin words for “most rough” or “most severe.”

Description: The Rough Clam Shell has a circular to oval profile, is thin in structure, and is moderately inflated. The shell is sculpted with 36 to 40 slightly rounded radial ribs, which are crossed with fine commarginal striae that may only be visible at the posterior end. The exterior of the shell is cream, tan, brown or white in color. Some specimens have darker bands, chevrons or maculations. The interior varies from bluish to purple or whitish.  Rough Clam Shells reach a maximum of 5.1 cm (2.0 inches) in length and 4.7 cm (1.8 inches) in height.

Habitat and Distribution: Rough Clams are found on sand or muddy sand, in the intertidal zone, and to depths up to 16 m (52 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 the west coast of the Baja Peninsula.

Ecology and Behavior:  Rough Clams are suspension feeders that feed primarily on planktonic algae such as cyanobacteria, diatoms, and dinoflagellates. In turn they are preyed upon by crabs, octopus, snails and starfish. They are gonochoric and reproduce sexually, through broadcast spawning, with external fertilization. From a conservation perspective the Rough 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. The Rough Clam is is edible and has been utilized as a food source for humans for thousands of years.

Synonyms: Prothaca asperrima and Venus asperrima.