Modest Periwinkle Shell, Echinolittorina modesta

Modest Periwinkle Shell, Echinolittorina modesta. Shell collected off the beach in the greater Los Cabos area, Baja California Sur., August 2009. Size: 1.5 cm (0.6 inches) x 1.0 cm (0.4 inches).

Phylogeny: The Modest Periwinkle, Echinolittorina modesta (Phillipi, 1846), is a gastropod mollusk that is a member of the Littorinidae Family of Periwinkle Shells. The genus Echinolittorina is one of seventeen genera in this family, and there are sixty-two species in this genus. They are known in Mexico as Litorina Modesta.

Description: Modest Periwinkle shells consist of five to six rounded whorls with a modestly pointed apex. The exterior is sculpted with a series of ridges following along the whorls. The shell is white in color, with reddish brown speckling or blotching. The aperture is light orange-brown. Some shells have apertures with dark brown markings. Modest Periwinkle Shells reach a maximum of 1.9 cm (0.8 inches) in length and 1.3 cm (0.5 inches) in width.

Habitat and Distribution: Modest Periwinkles are found along rocky shorelines, in the mid to high intertidal zone. They are a subtropical to tropical Eastern Pacific species that are found in Mexican waters of the Pacific Ocean from Ensenada, Baja California south to Guatemala. They are found in  the Sea of Cortez south of El Choyudo, Sonora.

Ecology and Behavior: Modest Periwinkles are herbivores that feed primarily on algae. They are gonochoric and reproduce sexually, through broadcast spawning, with external fertilization. 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: Littorina modesta, Littorina phillipi, Nodilittorina (Fossarlittorina) modesta, and Nodilittorina modesta.