Frilled Venus Clam Shell, Chione undatella

Frilled Venus Clam Shell, Chione undatella. Shell collected from within the estuary of the Magdalena Bay complex, Baja California Sur, October 2018. Size: 4.0 cm (1.6 inches) x 3.6 cm (1.4 inches).  Identification courtesy of Bob Hillis, Ivins, Utah.

Phylogeny: The Frilled Venus Clam, Chione undatella (G.B. Sowerby I, 1835), is a bivalve mollusk that is a member of the Veneridae Family of Venus Clam Shells. The genus Chione is one of one hundred seven genera in this family, and there are eleven species in this genus. They are also known as the Wavy Chione and in Mexico as Almeja de Costillas Ondeadas, Almeja Ronosa del Mar de Cortez, and Venus Reñosa.

Description: The Frilled Venus Clam shell is thick and moderately inflated,  with an oval or trigonal outline. The exterior is sculpted with closely spaced concentric ridges, and low, broad, radial ridges. They have a short siphon and a well-developed foot. The exterior of the shell is whitish with brown blotches, chevrons, or broken, radiating, bands, The interior is white with purple near the posterior end. The Frilled Venus Shells reach 6.6 cm (2.6 inches) in length and 5.9 cm (2.3 inches) in height.

Habitat and Distribution: Frilled Venus Clams reside in shallow burrows within firm sand and sandy mud bottoms. They live intertidally, and to depths up to 90 m (300 feet). They are found in bays and other places where they are protected from wave action and strong currents. They are a subtropical to tropical Eastern Pacific species. In Mexican waters they are found along the entire west coast,  including the Revillagigedo Islands and throughout the Gulf of California.

Ecology and Behavior:  Frilled Venus Clams are infaunal suspension feeders that feed primarily on planktonic algae and suspended organic matter. Their predators include fish, crabs, sea stars, and shore birds. They are gonochoric and reproduce sexually, through broadcast spawning, with external fertilization. The Onyx Slipper Limpet Shell, Crepidula onyx, is a known epibiont on this species.  Frilled Venus Clams are edible, and are subject to artisanal, commercial, and recreational harvesting.  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: Chione simillima, Chione undatella taberi, Venus entobapta, Venus( Chione) excavata, Venus neglecta, Venus perdix, Venus simillima, and Venus undatella.