Robust Auger Shell, Terebra robusta

Robust Auger Shell, Terebra robusta. Shell collected from the beaches of the greater Los Cabos area, Baja California Sur, March 2008. Size: 5.7 cm (2.2 inches) x 1.3 cm (0.5 inches). Identification courtesy of Bob Hillis, Ivins, Utah.

Phylogeny: The Robust Auger Shell, Terebra robusta (Hinds, 1844),  is a gastropod mollusk that is a member of the Terebridae Family of Augers. The genus Terebra is one of nineteen genera in this family, and there are one hundred eighteen species in this genus. They are known in Mexico as Taladro Robusto.

Description: Robust Auger Shells are solid and have a very high spire. Overall, they are narrow and elongate, but some individuals are more slender or broad than others. They consist of fifteen to eighteen fairly flat-sided whorls. Each whorl has a groove above its center line.  The whorls are well sculpted with lengthwise ridges that become less pronounced with maturity and in later whorls. They have a small, elongate, aperture. The columella is recurved and has one fold. The exterior of the shell is white to yellowish in color, with chestnut spots that often join to form oblique or wavy axial lines. The interior is white. They do not have a periostracum. Robust Auger Shells reach a maximum of 15.5 cm (6.1 inches) in length and 3.5 cm (1.4 inches) in height.

Habitat and Distribution: Robust Auger Shells are found on mud, rubble and sand substrates. They live in the intertidal zone, and to depths up to 110 m (360 feet). They are a subtropical to tropical Eastern Pacific species. In Mexican waters they range from Bahía Santa Maria, Baja California Sur, to Guatemala, including the Tres Marias Islands. They are found throughout the Gulf of California.

Ecology and Behavior: Robust Auger Shells are a poorly studied and understood species. There is very limited documentation of their diet, predation, reproduction or ecosystem interactions. Other species in Family Terebridae are predators that feed primarily on polychaete worms. They are gonochoric and reproduce sexually, with internal fertilization. The eggs are laid in protective capsules. 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 considered to be of Least Concern.

Synonyms: Terebra dumbauldi, Terebra insignis, and Terebra loroisii.