Tergina Dwarf Olive Shell, Olivella tergina

Tergina Dwarf Olive Shell, Olivella tergina. Shell collected off the beach in the greater Los Cabos area, Baja California Sur, May 2009. Size: 1.7 cm (0.7 inches) x 0.7 cm (0.3 inches).

Phylogeny: The Tergina Dwarf Olive Shell, Olivella tergina (Duclos, 1835), is a gastropod mollusk that is a  member of the Olividae Family of Olives. The genus Olivella is one of eleven genera in this family, and there are one hundred fifteen species in this genus.

Description: Tergina Dwarf Olive Shells are small, have five whorls, and a pointed apex. The aperture extends about half the length of the shell and it widens as it approaches the anterior end. The exterior of the shell is smooth and gray, light brown, or dark brown in color with white triangular markings. The inner lip of the aperture is sculpted with 6-9 grooves. The interior may be white, brown, gray, orangish, bluish, or purple. Tergina Dwarf Olive Shells reach a maximum of 1.8 cm (0.7 inches) in length and 0.7 cm (0.3 inches) in height.

Habitat and Distribution: Tergina Dwarfs reside on sand in the intertidal zone and to depths of 27 m (89 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 Magdalena Bay, Baja California Sur along the central and northwest coasts of the Baja Peninsula and north of Cabo Pulmo, Baja California Sur, in the Sea of Cortez.

Ecology and Behavior: Tergina Dwarf Olives are a poorly studied and understood species. There is very limited documentation of their diet, predation, reproduction or ecosystem interactions. Other species in the Olivella Genus may be predatory carnivores, suspension feeders, or depositional feeders. They are gonochoric and reproduce sexually with internal fertilization. The eggs are laid in protective capsules. Their engagement in any type of commensal, parasitic or symbiotic relationship has not been formally documented. From a conservation perspective the Tergina Dwarf Olive has 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 tergina.