Panama Thorny Cockle Shell, Dallocardia radula

Panama Thorny Cockle Shell, Dallocardia radula. Shell collected off the beach at Km 26, Cero Colorado, Baja California Sur, March 2010. Size: 2.6 cm (1.0 inch) x 2.6 cm (1.0 inch).

Phylogeny: The Panama Thorny Cockle, Dallocardia radula (Broderip and G.B. Sowerby I, 1833), is a bivalve mollusk that is a member of the Cardiidae Family of Cockles and True Cockle Shells. The genus Dallocardia is one of forty-nine genera in this family, and there are four species in this genus. This species seems to go back and forth between the names Dallocardia senticosa and Dallocardia radula, and many sources are not in agreement.  The World Registry of Marine Species (Worms) currently shows Dallocardia radula to be the currently accepted species name.

Description: The Panama Thorny Cockle shell is inflated and has a circular profile. The exterior is sculpted with numerous radiating ribs. At both ends of the shell and the anterior portion, these ribs display spathate (spatula-like) scales. These shells are whitish with reddish, pink or purple blotches. The inside is white with pink or purple at the hinge. Panama Thorny Cockles reach a maximum of 6.0 cm (2.4 inches) in height and 5.7 cm (2.2 inches) in length.

Habitat and Distribution: The Panama Thorny Cockle is found on, and within, sand and mud substrates from the intertidal zone and to depths up to 91 m (300 feet). They are a subtropical to tropical Eastern Pacific species that are found in all Mexican waters of the Pacific Ocean with the exception that they are absent from west coast of the Baja Peninsula.

Ecology and Behavior: Panama Thorny Cockles are suspension feeders that feed primarily on plankton and other 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 consider to be of Least Concern.

Synonyms: Cardium radula, Cardium rastrum, Cardium senticosum, Dallocardia senticosa, and Trachycardium senticosum.