Polpast Olive Shell, Oliva polpasta

Polpast Olive Shell, Oliva polpasta. Shell collected off the beach in the greater Los Cabos area, Baja California Sur, November 2016. Size: 4.8 cm (1.9 inches) x 2.8 cm (1.1 inches).

Phylogeny: The Polpast Olive Shell, Oliva polpasta (Duclos, 1833), is a gastropod mollusk that is a member of the Olividae Family of Olive Shells. The genus Oliva is one of eleven genera in this family, and there are one hundred and twenty species in this genus. There are two currently recognized subspecies, Oliva polpasta polpasta and Oliva polpasta radix.

Description: The Polpast Olive Shell is sturdy, cone-shaped, and consists of five whorls. It has a moderately high and pointed spire. The inside lip of the aperture wraps around the base of the shell and is marked with several grooves. The exterior of the shell is shiny gray, with numerous brown specks, spots and chevrons; the interior is white to cream. Polpast Olive Shells reach a maximum of 5.0 cm (2.0 inches) in length and 2.9 cm (1.1 inches) in height.

Habitat and Distribution: Polpast Olives are found on and within sand substrate from the intertidal zone to depths up to 35 m (115 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 Bahía de Los Ángeles, Baja California, in the Sea of Cortez.

Ecology and Behavior: Polpast Olives are predatory carnivores. They are ambush predators, remaining hidden in the sand until prey is detected and then quickly engulfed by the olive’s large foot. They eat bivalves, small invertebrates and detritus. In turn they are preyed upon by fish and gastropods. 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 Polpast 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: Americoliva polpasta, Oliva (Americoliva) polpasta, Oliva callosa, and Oliva davisae.