Delesserti Bittersweet Shell, Axinactis delessertii

Delesserti Bittersweet Shell, Axinactis delessertii. Size: 2.8 cm (1.1 inches) x 2.7 cm (1.1 inches). Shell collected off the beach at Km 26, Cero Colorado, Baja California Sur, March 2010.

Phylogeny: The Delesserti Bittersweet Shell, Axinactis delessertii (Reeve, 1843), is bivalve mollusk that is a member of the Glycymerididae Family of Bittersweet Shells. The genus Axinactis is one of four genera in this family, and there are only two species in this genus. The family name comes from the ancient Greek word glykymaris, which means “sweet part”.

Description: The Delesserti Bittersweet Shell is inflated, equivalve, and has a round profile. The outside is marked with strong, wide, serrated ribs, separated by finer ribs. The exterior of the shell is white outside with brown, zigzagging, transverse bands. The interior is white with a brownish mark at the footprint of the posterior adductor muscle. Delesserti’s Bittersweet Shells reach a maximum of 4.5 cm (1.8 inches) in length and 4.3 cm (1.7 inches) in height.

Habitat and Distribution: Delesserti’s Bittersweet Shells are found on sand and mud bottoms at depths between 8 m (25 feet) and 34 m (110 feet). They are a subtropical to tropical Eastern Pacific species. In Mexican waters they range from Magdalena Bay, Baja California Sur to Guatemala. This species is not known form the Gulf of California.

Ecology and Behavior:  Delesserti’s Bittersweet Shells are suspension feeders that feed primarily on planktonic algae and suspended organic matter. They are gonochoric and reproduce sexually, through broadcast spawning. 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: Pentunculus delessertii.