About Littorina obtusata (Linnaeus, 1758)
Littorina obtusata, commonly called Flat Periwinkles, are marine sea snails that use gill respiration. They can reach a height of 1.5 cm, with the maximum recorded shell length being 13.5 mm. Their shells can appear brown, yellow, olive green, or black, with most individuals being brown, reddish brown, or yellow, and few individuals being red or white, a variation linked to the abundance of brown seaweed where they live. They get their common name from their flattened spire and large tear-drop shaped aperture; the last whorl of their shell accounts for 90% of the shell's total height. Because of their gill respiration, this mainly littoral species can survive both in water and for extended periods of time out of water on land. This marine species is found wherever brown seaweeds grow, and it has a wide distribution: it occurs in the Baltic Sea, in European waters from Norway down to Southern Spain, in the Mediterranean Sea, and in the Northeast Atlantic Ocean along the Gulf of Maine. This species inhabits the littoral and sublittoral zones of rocky shores and piers, and is usually found on brown algae of the genus Fucus. It occurs from a minimum recorded depth of 0 m to a maximum recorded depth of 110 m. The color of an individual is often shaped by its habitat: individuals on sheltered shores have lighter, uniform colors such as yellow, brown, orange, or olive green, while individuals on exposed shores have darker, chequered coloration. This species is tolerant of low salinities and a wide range of exposure conditions. Female Littorina obtusata deposit spawn masses on Ascophyllum nodosum, Fucus serratus, Fucus vesiculosus, and sometimes on rock surfaces. Their eggs are whitish, and can be either oval or kidney-shaped. Each egg is encased in a mass of transparent jelly. Eggs take up to four weeks to fully develop before young snails emerge. Individuals reach sexual maturity at around two years of age. The species reproduces year-round, with peak reproduction occurring from spring to fall.
