Angle-mouth Screw Shell, Caviturritella gonostoma

Angle-mouth Screw Shell, Caviturritella gonostoma. Shell collected off the beach in the greater Punta Chivato area, Baja California Sur, December 2022.  Size: 12.7 cm (4.9 inches) x 2.8 cm (1.8 inches). Photograph and Identification courtesy of Colin Campbell, DVM, Punta Chivato, Baja California Sur.

Phylogeny: The Angle-mouth Screw Shell, Caviturritella gonostoma (Vallenciennes, 1832), is a gastropod mollusk that is a member of the Turretellidae Family of Turrets or Tower Shells. The genus Caviturritella is one of twenty-four genera in this family, and there are four species in this genus.

Description: Angle-mouth Screw Shell Shells are solidly built shells with many flat-sided whorls wand a small aperture. The exterior is sculpted with fine spiral lines with younger specimens having a spiral ridge in the middle of the whorl that disappears with maturity. The exterior of the shell is gray to purplish brown in color, with white mottling. The Angle-mouth Screw Shell is one of the larger Turrets in the area reaching a maximum of 16.3 cm (6.4 inches) in length and 3.5 cm (1.4 inches) in height.

Habitat and Distribution: Angle-mouth Screws are found on and within mud and sand substrate from the intertidal zone to depths up to 6 m (20 feet). They are a 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 Bahía San Juanico, Baja California Sur, along the central and northwest coasts of the Baja Peninsula.

Ecology and Behavior: Species in the Turretellidae Family are suspension feeders, using mucous strings to capture plankton and suspended organic matter. They are preyed upon by crabs and other gastropods, especially Moon Snails and Murexes. They are known to host parasitic trematodes. Angle-mouth Screw Shells are gonochoric. Reproduction is sexual, with internal fertilization.  Their eggs  laid in a cluster of spherical, stalked capsules. From a conservation perspective the Angle-mouth Screw 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: Turritella goniostoma, Turritella gonostoma, and Turritella punctata.