Edible Periwinkle

The flat periwinkle grazes on detritus and microorganisms. It also feeds on green seaweeds such as sea lettuce (Ulva lactua) and species of Enteromorpha (2). Breeding may take place throughout the year, but tends to vary depending on temperature (4). The sexes are separate (individuals are either male or female), and fertilisation occurs internally after copulation (2). Egg laying is timed to coincide with the spring tide; the eggs are laid in the sea in gelatinous capsules that usually contain around three eggs (although up to 9 eggs per capsule has been known) (4). The egg capsules float in the sea and free-swimming 'veliger' larvae hatch after a few days. After 6 weeks spent in the ocean, the larvae settle on the shore. The young periwinkles attain sexual maturity at two or three years of age and may live for up to five years (2).

Not relevant.

Periwinkles are a large family of gastropod molluscs found on the shore. The edible periwinkle is perhaps the best known species of this family, as it has been collected and eaten for centuries. After boiling, the soft body is 'winkled out' from the shell with a pin or a special 'winkle-picker' (3). This species is the largest periwinkle found in Britain. It has a dark grey or black conical shell that develops a smooth surface with age. The flattened tentacles bear obvious black bands, a feature which allows young specimens to be identified easily. Males can be distinguished during the breeding season by the presence of a penis on the right side of the body (4).

This periwinkle is found from the upper shore down to the sublittoral and may also occur on mudflats and in estuaries (2). Large aggregations may arise in more suitable areas, such as rock-pools (4).

Common on all rocky British coasts, but is absent from the Channel Isles and Isles of Scilly (4). Elsewhere it is found around north-west Europe (2).

Not threatened (2).

This species is not threatened.