Angled Olive Shell, Oliva increassata

Angled Olive Shell, Oliva incrassata. Shell collected off the beach in the greater Los Cabos area, Baja California Sur, May 218. Size: 5.0 cm (2.0 inches) x 2.5 cm (1.0 inch).

Phylogeny: The Angled Olive, Oliva incrassata (Lightfoot, 1786), 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. They are also known as the Giant Olive or Angulate Olive and in Mexico as Oliva Angulosa. They derive their common name from the way the top of the outer lip angles toward the spire.

Description: Angled Olive Shells are thick and solid, with a somewhat swollen profile, and a noticeable ridge where the body whorl meets the spire. They have an apex that is sharply pointed and an aperture that is wider than that of most other Olives. They lack a periostracum and an operculum. The anterior of the body whorl is marked by ridges spiraling from the interior. The highly polished exterior of the shell can be white, cream, yellowish-gray, or light tan, with dark gray or brown specks, spots or chevrons; the interior is white. Angled Olive Shells reach a maximum of 9.5 cm (3.7 inches) in length and 4.8 cm (1.9 inches) in height.

Habitat and Distribution: Angled Olives are found over and within sand or sandy mud substrate from the intertidal zone to depths up to 90 m (300 feet). They are a tropical Eastern Pacific species that are found in all Mexican waters of the Pacific Ocean with the exception that they absent from north of Magdalena Bay, Baja California Sur, along the central and northwest coasts of the Baja Peninsula.

Ecology and Behavior: Species in the Olividae Family 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. Olive shells are primarily eaten 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 Angled Olive 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: Oliva angulata, Oliva angulata f. nivea, Oliva burchorum, Oliva incrassata f. burchorum, Oliva nivea, and Voluta incrassata.