Details
Littorina littorea
Common periwinkle is a small North Atlantic intertidal snail that clings to rocks through waves and drying air. It is a familiar grazer in intertidal food webs and helps shape algal films.
Map: Ecoregions 2017 © RESOLVE (CC BY 4.0) · Natural Earth (PD)
It lives on rocky shores, tide pools, breakwaters, and seaweed-rich intertidal zones of the North Atlantic. Main habitat types in this guide are coast, reef.
Typical length 1-3 cm, weight 1 g-5 g. A dark conical shell and a closing operculum help it resist drying.
It is active in repeated bouts across day and night and often found in loose groups. It crawls over rock and seaweed when covered by tide and closes up when exposed.
It is herbivorous. Microalgae are scraped from rock and seaweed surfaces with the radula.
Eggs enter the sea, and larvae drift as plankton before settling.
Although still widespread in places, it remains sensitive to habitat change. It is a familiar grazer in intertidal food webs and helps shape algal films.
