Littorina

Littorina is a genus of small to medium-sized marine snails in the family Littorinidae, commonly known as periwinkles. These gastropods are primarily grazers that inhabit the intertidal zone of shores worldwide. Shells are typically sturdy and conical to ovate, often with color patterns ranging from plain to striped, and they possess a well-developed operculum.

Habitat and distribution: Littorina species are most commonly found on rocky shores and other hard substrates in the intertidal zone. They tolerate immersion during high tides and desiccation during low tides, retreating to crevices or under stones when exposed. The genus has a broad distribution in temperate and subtropical regions of Europe, Asia, Africa, and the Americas. A notable introduced species is Littorina littorea, the common periwinkle, which has been introduced to North America in the 19th century.

Ecology: They are primarily herbivores, feeding on microalgae and biofilms on rocks, using a rasping radula. Their feeding and movement influence algal communities and microhabitat structure on rocky shores. Many Littorina species exhibit vertical zonation, occupying different tidal heights in accordance with their tolerance to immersion, desiccation, and temperature fluctuations.

Taxonomy and diversity: The genus Littorina has been subject to taxonomic revision, and genetic studies have led to reclassification of several species into related genera such as Nodilittorina and Austrolittorina. Despite changes, the group remains a key component of intertidal ecosystems and a common subject of ecological and evolutionary research.