Smooth Venus Clam Shell, Chionista fluctigraga

Smooth Venus Clam, Chionista fluctifraga.  Shell collected from within the estuary of the Magdalena Bay complex, Baja California Sur, October 2018. Size: 3.9 cm (1.5 inches) x 3.4 cm (1.3 inches).

Phylogeny: The Smooth Venus Clam Shell, Chionista fluctifraga (G.B. Sowerby II, 1853), is a bivalve mollusk that is a member of the Veneridae Family of Venus Clam Shells. The genus Chionista is one of one hundred and seven genera in this family, and this is the only species in this genus. They are also known as the Hard Shell Cockle.

Description: Smooth Venus Clam Shells are thick and somewhat inflated, with a rounded triangular outline. They are equivalve (both valves equal in size and shape), with short siphons. There are three cardinal teeth at the hinge. The exterior of the shell has both radial ribs and concentric ridges, with more pronounced radial ribs at the posterior end. The anterior margin of the shell is lightly serrated. The exterior of the shell is cream or white in color, sometimes having purple maculations. The interior is white, often with purple blush. Smooth Venus Clam Shells reach a maximum of 8.7 cm (3.4 inches) in length and 7.6 cm (3.0 inches) in height.

Habitat and Distribution: Smooth Venus Clams live in shallow burrows within sand and mud substrates within the intertidal zone, and at depths up to 31 m (80 feet). They are a subtropical Eastern Pacific species that are found in all Mexican waters of the Pacific Oceran with the exception that they are absent from coastal waters of the mainland south of Manzanillo, Colima.

Ecology and Behavior: Smooth Venus Clam Shells are suspension feeders, which feed on plankton and suspended organic matter. They are prey for shorebirds, crabs, fish, and gastropods. Smooth Venus Clam Shells are gonochoric and reproduce sexually, through broadcast spawning. They are known to host parasitic burrowing worms from the genus Polydora. They have a commensal relationship with the annelid worm Chaetogaster limnaei. From a conservation perspective the Smooth Venus Clam Shell has not been formally evaluated. However, they are fairly common with a relatively wide distribution and should be considered to be of Least Concern. The Smooth Venus Calm is edible and fished and farmed commercially.

Synonyms: Chione fluctifraga, Chione gibbosula, Venus cortezi, and Venus fluctifraga.