Purple Dwarf Olive Shell, Callianax biplicata

Purple Dwarf Olive Shell, Callianax biplicata. Shell collected off the beach of La Jolla, California October 2019. Size: 3.2 cm (1.3 inches) x 1.7 cm (0.7 inches).  Collection, photograph and identification courtesy of Bob Hillis, Ivins, Utah.

Phylogeny: The Purple Dwarf Olive Shell,  (G.B. Sowerby I, 1825), is a gastropod mollusk that is a member of the Olividae Family of Olives. The genus Callianax is one of eleven genera in this family, and there are four species in this genus. They are also known as the Two-plated Dwarf Olive.

Description: Purple Dwarf Olive Shells have about 4 whorls that are marked with a dark line. They have a large spire that has a larger spire to body ratio than most olive shells. Their apex is pointed. The aperture is wider at the bottom than at the top, and it has two folds at the base of the inner lip. The exterior dorsal surface of the shell is bluish gray, brown or white. The anterior is often white. The interior is white with purple blush and and a dark line along the inside edge of the outer lip. Purple Dwarf Olive Shells reach a maximum of 3.8 cm (1.5 inches) in length and 2.0 cm (0.8 inches) in height.

Habitat and Distribution: Purple Dwarf Olive Shells reside on clean sand. They are found, in large groups, at the entrance to lagoons and on protected open coasts. They live in the intertidal zone, and to depths up to 50 m (165 feet). They are a temperate to subtropical Eastern Pacific species. They have a limited range in Mexican waters. They are found along the west coast of the Baja Peninsula, from the northern border to Magdalena Bay, Baja California Sur. They are not found in the Gulf of California. These shells have been found in abundance in archaeological sites ranging from the coast to the Great Basin and the Desert Southwest of the United States. Beads made from these shells have served as currency via many cultures for centuries.

Ecology and Behavior: Purple Dwarf Olive Shells are omnivores that eat algae, small invertebrates, carrion, and detritus . Purple Dwarf Olive Shells are primarily eaten by sea stars, octopuses, shore birds and gastropods. They are gonochoric and reproduce sexually with internal fertilization. Mating can take up to 3 days. The male temporarily glues himself to the female during this time. The eggs are laid in protective capsules. They can live up to 15 years. They are known to host endo parasitic trematode larvae. There is no mention in the available literature of them engaging in any types of commensal or symbiotic relationships. From a conservation perspective  Purple Dwarf Olive Shells  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: Oliva biplicata, Olivella biplicata, Olivella biplicata angelena, Olivella biplicata lapillus, Olivella biplicata var. fucana, and Olivella biplicata var. parva.