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Flat periwinkle

Paul Naylor

Flat periwinkle

Scientific name: Littorina obtusata/fabalis
These little sea snails are found amongst the seaweed on rocky shores around much of the UK. They come in lots of different colours, from bright yellow to chequered brown!

Species information

Statistics

Height: Up to 1.5cm

Conservation status

Common

When to see

January to December

About

Found amongst the seaweeds on which it feeds, the flat periwinkle lives on the lower parts of the shore. It is most commonly associated with Bladder Wrack seaweed and can be mistaken for the air bladders that makes the seaweed float.

They come in lots of different colours, including orange, bright yellow, banded brown and a sort of olive green that makes them hard to spot amongst their seaweed home.

How to identify

There are actually two species of flat periwinkle but we can’t identify them without dissecting them. When recording the flat periwinkle as part of a recording scheme it is important to record them as Littorina obtusata/fabalis . And make sure to include clear photos to help verifiers confirm your sighting.

Distribution

Found on rocky shores all around our coasts, but absent from most of Lincolnshire and East Anglia.

Habitats

Did you know?

Periwinkles are able seal themselves into their shell by closing the 'door' - a round operculum. Flat periwinkles can breed throughout the year and have both male and female forms. Eggs are internally fertilised and laid on seaweed in masses of up to 280 eggs.

How people can help

When rockpooling, be careful to leave everything as you found it - replace any rocks you turn over, put back any crabs or fish and ensure not to scrape anything off its rocky home.