Similar Cardita Shell, Carditamera affinis
Similar Cardita Shell, Carditamera affinis. Shell collected off the beach at Km 26, Cero Colorado, Baja California Sur, March 2010. Size: 3.7 cm (1.5 inches) x 2.0 cm (0.8 inches).
Similar Cardita Shell, Carditamera affinis. Shell collected off the beach in the greater Punta Chivato area, Baja California Sur, December 2022. Size: 5.1 cm (2.0 inches) x 2.6 cm (1.0 inches) x 1.0 cm (0.4 inches). Photograph and Identification courtesy of Colin Campbell, DVM, Punta Chivato, Baja California Sur.
Phylogeny: The Similar Cardita Shell, Carditamera affinis (G.B. Sowerby I, 1833), is a bivalve mollusk that is a member of the Carditidae Family of Little Heart Shells. The genus Carditimera is one of thirty-seven genera in this family, and there are eight species in this genus. The name Carditamera comes from the Greek words, which mean “part of Cardita.” Affinis means neighboring, similar to, or akin to.
Description: Similar Cardita Shells are equivalve, inflated, and have a rounded trapezoidal outline. The anterior is sharply rounded. The posterior is longer, and rounded or truncate. The exterior is sculpted with 12-15 radial ribs, crossed by irregular commarginal ribs, which may give the shell a scaly texture. The exterior of the shell is yellowish brown to dark brown in color and the interior is white with brown to black margins. They have a dark brown periostracum. Similar Cardita Shells reach a maximum of 10 cm (3.9 inches) in length and 5.4 cm (2.2 inches) in height. These shells are similar in appearance to the Bajaensis Cardita Shell, Carditamera bajaensis, and most easily distinguished by habitat; the Bajaensis Cardita is found buried or partially buried in sand, mud, or loose gravel, while the Smilar Cardita is found on top of hard substrates or in rock crevasses.
Habitat and Distribution: Similar Carditas are found on rocks and rubble in 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 north of Punta Pequena, Baja California Sur along the central and northwest coasts of the Baja Peninsula.
Ecology and Behavior: Similar Carditas 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. Their engagement in any type of commensal, parasitic, or symbiotic relationship has not been formally documented. From a conservation perspective the Alternating Ark has not been formally evaluated. However, they are fairly common with a relatively wide distribution and should be considered to be of Least Concern.
Synonyms: Cardita affinis, Cardita californica, Cardita incerta, Cardita pectunculus, Cardita picta, and Cardita volucris.