Golden Callista Shell, Megapitaria aurantiaca

Golden Callista Shell, Megapitaria aurantiaca. Shell collected off the beach at Punta Chivato, Baja California Sur, January 2023. Size: 9.7 cm (3.8 inches) x 8.7 cm (3.4 inches) x 3.3 cm (1.3 inches). Collection, photographs and identifications courtesy of Colin Campbell, DVM, Punta Chivato, Baja California Sur.

Golden Callista Shell, Megapitaria aurantiaca. Shell collected off the beach at Punta Chivato, Baja California Sur, January 2023. Size: 10.6 cm (4.1 inches) x 10.0 cm (3.9 inches) x 7.0 cm (2.8 inches). Collection, photographs and identifications courtesy of Colin Campbell, DVM, Punta Chivato, Baja California Sur.

Phylogeny: The Golden Callista Clam, Megapitaria aurantiaca (G.B. Sowerby I, 1831), is a bivalve mollusk that is a member of the Veneridae Family of Venus Clam Shells. The genus Megapitaria is one of one hundred seven genera in this family, and there are three species in this genus. This species is also known as the Red Clam,  the Golden Clam, and the Golden Callista. They are known in Mexico as Almeja Reina Roja.

Description: The Golden Callista Clam shell is thick and solid, with a subovate outline. The anterior end of the shell is short and evenly rounded; the posterior end is longer and more sharply rounded. The shell is very inflated. The external surface has very fine commarginal lines or may appear smooth. The exterior color of the shell may be pink, pinkish-brown, pinkish-gray, cream, or orange. Some specimens have dark colored chevrons. The periostracum is thick, and brown to burnt orange in color. The interior is white, often with purple at the hinge plate. Golden Clams reach a maximum of 12.8 cm (5.0 inches) in length and 12.1 cm (4.8 inches) in height.

Habitat and Distribution: Golden Callista Clams are found buried in sand from the low intertidal zone to depths up to 30 m (98 feet). They are a subtropical to tropical Eastern Pacific species that are found in Mexican waters of the Pacific from Guerrero Negro, Baja California south to Guatemala. They are found throughout the Sea of Cortez.

Ecology and Behavior:  Golden Callista Clams are suspension feeders that feed primarily on planktonic algae and suspended organic matter. They are generally gonochoric, though some individuals are reported to be hermaphroditic. They reproduce sexually, through broadcast spawning, with external fertilization. There is no mention in the available literature of them engaging in any types of parasitic, commensal, or symbiotic relationships. They are edible and are targeted by artisanal, recreational, and commercial fisheries. 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: Callista aurantiaca, Cytherea aurantiaca, and Cytherea livida.