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 Clam Shells 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. In Mexican waters they are found throughout the Gulf of California and range south along the coastline to Guatemala. They have not been documented along the west coast of the Baja Peninsula.

Ecology and Behavior:  Rough Clam Shells are suspension feeders that feed primarily on planktonic algae such as dinoflagellates, diatoms, and cyanobacteria.  They are prey for crabs, starfishes, predatory snails, and octopuses. They are gonochoric and reproduce sexually, through broadcast spawning, with external fertilization. This species is edible and has been utilized as a food source for thousands of years. 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: Prothaca asperrima and Venus asperrima.