Common Periwinkle
Littorina littorea
Habitat: Rocky shore and rock pools to low shore
Depth: 1-60m
Food: Algae covering the rocks
Size: Up to 4cm
Lifespan: Unknown
Conservation Status: Not Evaluated (NE)
Familiar to all rock-poolers, this little sea snail is very common on the rocky shore, but also in muddy areas such as estuaries. Periwinkles are herbivorous, grazing algae by scraping it with their radula – a tongue-like structure covered in teeth. When the tide goes out, periwinkles can close off their shell with a trap door, to keep moist inside.