Carved Donax Clam Shell, Donax caelatus

Carved Donax Clam Shell, Donax caelatus. Shell collected off the beach at Punta Chivato, Baja California Sur, April 2025. Size: 1.7 cm (0.7 inches) x 1.1 cm (0.4 inches) x 0.9 cm (0.4 inches). Collection, photograph and Identification courtesy of Colin Campbell, DVM, Punta Chivato, Baja California Sur.

Phylogeny: The Carved Donax Clam Shell, Donax caelatus Carpenter, 1857, 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 Tallada.

Description: Carved Donax Clam Shells are  trigonal to elliptical outline. They are inflated in profile. The shell is about one and a half times as long as it is high. The anterior end is longer and more rounded than the posterior. The posterior end is set off by a strong ridge and is somewhat truncate (appearing chopped off) toward the ventral margin. The exterior of the shell is sculpted with low radial ribs. The posterior end has commarginal grooves between the ribs. The interior margin has fine “teeth” that do not extend to the margin. The exterior of the shell may be tan, reddish, or purple in color. The interior is white, often with a pink or purple blush. Carved Donax Clam Shells reach a maximum of 4.9 cm (1.9 inches) in length.

Habitat and Distribution: Carved Donax Clam Shells are found buried beneath the surface of sand substrates, from the intertidal zone to depths of around 3 m (10 feet). Carved Donax Clam Shells are a subtropical to tropical Eastern Pacific species. In Mexican waters, they range from Bahía de Las Ánimas, Baja California, to Guatemala. They are absent from the extreme north end of the Gulf of California, and from the west coast of the Baja Peninsula.

Ecology and Behavior: Carved Donax Clam Shells 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. Their engagement in any type of commensal, parasitic, or mutualistic relationship has not been formally documented. The Carved Donax Clam Shell 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 (Chion) caelatus and Donax punctatostriatus var. caelatus.