California Beanclam Shell, Donax californicus

California Beanclam Shell, Donax californicus. Shell collected off the beach at Punta Chivato, Baja California Sur, May 2025. Size: 2.1 cm (0.8 inches) x 1.0 cm (0.4 inches) x 0.4 cm (0.2 inches). Collection, photograph and Identification courtesy of Colin Campbell, DVM, Punta Chivato, Baja California Sur.

California Beanclam Shell, Donax californicus. California Beanclam Shell, Donax californicus. Shell collected off the beach at Punta Chivato, Baja California Sur, May 2025. Size: 2.4 cm (0.9 inches) x 1.2 cm (0.5 inches) x 0.5 cm (0.2 inches). Collection, photograph and Identification courtesy of Colin Campbell, DVM, Punta Chivato, Baja California Sur.

Phylogeny: The California Beanclam, Donax californicus (Conrad 1837), is a bivalve mollusk in the Donacidae Family of Donax Clam Shells. The Donax Genus is one of five genera in the Donacidae Family, and there are sixty-nine species in the Donax Genus. They are known In Mexico as Coquina Amarilla.

Description: The California Beanclam Shell is moderately inflated and has a trigonal to elliptical outline. The shell is about twice as long as it is high. The anterior is end is longer and more widely rounded than the posterior. The posterior end is set off by a rounded ridge. The ventral margin is not evenly rounded, with a curve anterior to the beaks. The exterior of the shell may be smooth or sculpted with fine radial striae.  The interior margin has fine “teeth” that do not extend to the margin. The exterior of the shell is shiny and may be white, gray, tan or brown in color, often with darker colored commarginal bands. The interior is white, often with a purple wash and dark purple along the dorsal margin. The periostracum is thin and shiny. California Beanclam Shells reach a maximum of 3.3 cm (1.3 inches) in length.

Habitat and Distribution: California Beanclam Shells reside slightly buried beneath the surface of sand or muddy sand in bays or protected outer coastlines. They are found in the intertidal zone, and to depths up to 70 m (230 feet). California Beanclam Shells are a subtropical to tropical Eastern Pacific species. They are found along the entire west coast of Mexico, including the Gulf of California.

Ecology and Behavior: California Beanclams are suspension feeders that feed primarily on planktonic algae and suspended organic matter. They are prey for crabs, fish, and shorebirds. They are gonochoric and reproduce sexually, through broadcast spawning, with external fertilization. They are known to host the endoparasitic trematode Postmonorchis donacis. Their engagement in any type of commensal or mutualistic relationship has not been formally documented. The California Beanclam has not been formally evaluated from a conservation perspective. However, they are common, with a relatively wide distribution, and should be consider to be of Least Concern.

Synonyms: Donax (Paradonax) californicus, Donax californica, and Donax navicula.