Banded Periwinkle Shell, Littoraria variegata

Banded Periwinkle Shell, Littoraria variegata. Shell collected off the beach in the greater Los Cabos area, Baja California Sur. Size:  2.6 cm (1.0 inch) x 1.9 cm (0.7 inches).

Phylogeny: The Banded Periwinkle, Littoraria variegata (Souleyet, 1852), is a gastropod mollusk that is a member of the Littorinidae Family of Periwinkles. The genus Littoraria is one of seventeen genera in this family, and there are thirty-eight species in this genus. This species is also known as the Fasciate Periwinkle.

Description: The Banded Periwinkle Shell has five or six whorls, with the body whorl being large.  They have a sharply pointed apex and their exterior is sculpted with fine lines running along the whorls. There are oblique growth ridges running the length of the shell. The exterior of the shell is cream to golden brown in color, with darker brown speckles, lines, and/or blotches; the interior is cream to yellowish. Some specimens have a solid or interrupted brown line along the margin of the outer lip of the aperture. Banded Periwinkle Shells reach a maximum of 4.0 cm (1.6 inches) in length and 2.9 cm (1.2 inches) in height.

Habitat and Distribution: Banded Periwinkles are found attached to mangroves and on rocks in protected waters in the intertidal zone. 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 Magdalena Bay, Baja California Sur, along the central and northwest coasts of the Baja Peninsula.  Within the Sea of Cortez their range is limited by habitat.

Ecology and Behavior:  Banded Periwinkles are grazers that feed primarily on algae, fungi, diatoms, and mangrove leaf epidermis.  Their primary predators are crabs and shorebirds. They are gonochoric and reproduce sexually, with internal fertilization. The eggs are laid in protective capsules. This species is known to host endoparasitic trematodes. They’re engagement in any type of commensal or symbiotic relationships has not been formally documented. From a conservation perspective the Banded Periwinkle 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: Littoraria (Littoraria) variegata, Littorina fasciata, and Littoraria  variegata.