Day 6: Sea Snails

How to identify
Limpets are a common seashore sight, often attached to the side of rocks and rockpools, waiting for the tide to come in before they can move and feed. They eat algae, using their tongue to scrape it off the rocks.

There are three very similar species of limpet found on UK shores. The common limpet has a greyish, conical shell and is slightly larger than the other two - most differences are found on the underside of the shell. You must however never remove them from the rock to identify, but taking a photo can be a good way to study or ask advice on which type of limpet you’ve found.

Did you know?
Limpets move around over the rocks when the tide is in, but always return to their own favourite spot when the tide goes out, following the mucus trail that they have deposited. This spot becomes worn by the edges of the shell, and eventually an obvious 'scar' in the rock is created. This 'home scar' helps the limpet to better attach to the rock, stopping it drying out until the next tide comes in.

How to identify
This snail is often found on the lower parts of the shore, amongst seaweed, which is its source of food. It is most commonly associated with bladder wrack seaweed and can be mistaken for the air bladders that make the seaweed float.

Flat periwinkles come in many different colours including orange, bright yellow, banded brown and olive green. There are also two species of flat periwinkle but they can’t be identified externally, hence the obtusata/fabalis in their latin name. If recording this species it’s important to use both names. 

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 to identify
Dog whelks are usually found on the lower shore wherever there are barnacles or mussels - their favourite food, and once they have fed they will find a crevice in which to rest for a few days before feeding again. 

To identify, look for a conical shell with a pointed spire - predominately these are white but can also be brown or yellow. It is smaller than the common whelk, smoother than the netted whelk and more rounded than the oyster drill.

Did you know?
The dog whelk feeds on mussels and barnacles by boring through their shells. It then injects enzymes to digest the prey within its shell, sucking the resulting 'liquid soup' out through its proboscis. It can take days to eat its prey this way.