Lurid Ark Shell, Barbatia lurida

Lurid Ark Shell, Barbatia lurida. Shell collected from the beach at Punta Chivato, Baja California Sur, December 2022.  Size: 3.0 cm (1.2 inches) x 1.8 cm (0.7 inches) x 0.6 cm (0.2  inches). Collection, photograph and Identification courtesy of Colin Campbell, DVM, Punta Chivato, Baja California Sur.

Lurid Ark Shell, Barbatia lurida. Shell collected from the beach at Punta Chivato, Baja California Sur, December 2022.  Size: 6.2 cm (2.4 inches) x 3.7 cm (1.5 inches) x 1.2 cm (0.5  inches). Collection, photograph and Identification courtesy of Colin Campbell, DVM, Punta Chivato, Baja California Sur.

Phylogeny: The Lurid Ark, Barbatia lurida (G.B. Sowerby I, 1833), is a bivalve mollusk that is a member of the Arcidae Family of Ark Shells. The genus Barbatia is one of thirty-five genera in this family, and there are thirty-seven species in this genus. They are known in Mexico as Arca Lúrida. Ark shells obtain their name from their shell that has alternating teeth along the hinge that allow the shell to close securely. The species name Lurida comes from the Latin meaning sallow or yellowish tan.

Description: The Lurid Ark shell has an ovate shape with a rounded anterior, and a wider and sloped posterior end. The beak is wide and low. There are fine radiating lines across most of the shell. The anterior of the shell is tan in color. The posterior is dark brown to purplish in color. The interior is white to gray, often with purple tinting. According to many sources Lurid Ark Shells reach a maximum length of 5.1 cm (2.0 inches) in length, although Dr. Colin Campbell has found specimens that are 6.2 cm (2.4 inches) in length, and 3.7 cm (1.4 inches) in height.

Habitat and Distribution: Lurid Arks attach themselves to rocks with fine silky byssus, giving rise to their genus name – Barbatia (bearded one). This species lives intertidally and to depths up to 30 m (100 feet). Lurid Arks are a subtropical to tropical Eastern Pacific species that are found in Mexican waters of the Pacific Ocean from from the northern end of the Sea of Cortez south to Guatemala.

Ecology and Behavior: Lurid Arks are suspension feeders that feed primarily on planktonic algae and suspended organic matter. They are gonochoric and 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. From a conservation perspective they have not been formally evaluated however they are fairly common with a relatively wide distribution and should be considered to be of Least Concern.

Synonyms: Byssoarca lurida and Byssoarca vespertilio.