Pacific Calico Scallop Shell, Argopecten ventricosus
Pacific Calico Scallop Shell, Left Valve, Argopecten ventricosus. Size: 9.4 cm (3.7 inches) x 8.1 cm (3.2 inches). Shell collected from within the estuary of the Magdalena Bay complex, Baja California Sur, October 2018.
Pacific Calico Scallop Shell, Right Valve, Argopecten ventricosus. Size: 9.4 cm (3.7 inches) x 8.1 cm (3.2 inches). Shell collected from within the estuary of the Magdalena Bay complex, Baja California Sur, October 2018.
Pacific Calico Scallop Shell, Right Valve, Argopecten ventricosus. Size: 9.6 cm (3.8 inches) x 8.3 cm (3.3 inches). Shell collected from within the estuary of the Magdalena Bay complex, Baja California Sur, October 2018. Collection, photograph and identification courtesy of Bob Hillis, Ivins, Utah.
Pacific Calico Scallop Shell, Left Valve, Argopecten ventricosus. Size: 6.2 cm (2.4 inches) x 5.8 cm (2.3 inches). Shell collected from within the estuary of the Magdalena Bay complex, Baja California Sur, October 2018. Atypically colored. Identification courtesy of Bob Hillis, Ivins, Utah.
Phylogeny: The Pacific Calico Scallop, Argopecten ventricosus (G.B. Sowerby II, 1842), is a bivalve mollusk that is a member of the Pectinidae Family of Scallop Shells. The genus Argopecten is one of sixty-four genera in this family, and there are eight species in this genus. They are also known as the Catarina Clam, the Catarina Scallop and the Speckled Scallop and in Mexico as Almeja Catarina, Peine Volador and Vieira Jaspeada.
Description: The Pacific Calico Scallop shell has a round outline and is very inflated. The right valve is very convex and the left valve is moderately convex. The hinge is straight and has pronounced ears (auricles) that are about equal in size. The exterior of the shell has approximately twenty smooth, radiating ribs. The exterior of the shell is white with blotches or angular patterns of brown, maroon, orange, purple, or yellow and the interior is white. Pacific Calico Scallop shells reach a maximum of 11.0 cm (4.3 inches) in length and 9.0 cm (3.5 inches) in height.
Habitat and Distribution: Pacific Calico Scallops are found in shallow bays, sloughs, and calm, offshore areas, on and within mud and sand substrates and are often associated with eelgrass beds within the intertidal zone to depths up to 55 m (180 feet). They are a subtropical to tropical Eastern Pacific species that are found in all Mexican waters of the Pacific Ocean including the Sea of Cortez and the Revillagigedo Islands.
Ecology and Behavior: Pacific Calico Scallops 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. They are known to host several species of algae, mollusks, and barnacles on their shells as epibionts. They also commensally host the pinnotherid crab Tumidotheres margarita in their gills. They are edible and have been heavily fished in Baja California Sur for centuries and were over harvested in La Paz Bay to the point of commercial extinction by the mid-20th century. They are currently commercially fished heavily in Magdalena Bay by hookah divers with significant conservation efforts on-going to maintain a sustainable fishery. From a conservation perspective they have not been formally evaluated however they are fairly common with a very wide distribution and should be considered to be of Least Concern.
Synonyms: Argopecten circularis, Argopecten circularis calli, Argopecten ventricosus aequisulcatus, Pecten (Aequipecten) aequisulcatus, Pecten (Pecten) compactus, Pecten (Plagioctenium) calli, Pecten (Plagioctenium) newsomi, Pecten (Plagioctenium) subventricosus, Pecten aequisulcatus, Pecten fililextus, Pecten inca, Pecten newsomi, Pecten pomatia, Pecten solidulus, Pecten tumidus, Pecten ventricosus, and Pecten ventricosus var. aequisulcatus.