Great Ram’s-horn Snail

Planorbis corneus

SIZE AND DESCRIPTION

Shell diameter to 3.5cm; height to 1.2cm. The shape of the dark brown shell gives this large snail its common name. One of more than 50 snail species found in Britain.

HABITAT AND DISTRIBUTION

Ponds, lakes and slow-flowing rivers. Also found in garden ponds because it is sold by aquarium dealers. Native range is from Europe to central Asia.

FOOD AND HABITS

Feeds on algae on stones and plants. Its eggs, which are laid on stones, may be spread to other ponds whenever they stick to the feet of birds.

Great Pond Snail

Lymnaea stagnalis

SIZE AND DESCRIPTION

Shell height to 5cm; width to 2.5cm. Pointed spiral shell is yellowish to dark brown.

HABITAT AND DISTRIBUTION

Large, calcium-rich ponds, ditches, lakes and slow-flowing rivers and canals. The most common water snail in areas of hard water. Widely distributed across Europe, and common in many countries.

FOOD AND HABITS

Feeds on algae and decaying vegetation. Eggs are laid in a sausage-shaped gelatinous sac on the undersides of leaves.

Ear Pond Snail

Lymnaea auricularia

SIZE AND DESCRIPTION

Shell height to 3cm; width to 2.5cm. Shiny, rounded shell that is yellow, beige or tan. Ear-shaped aperture is very large and occupies four-fifths of the shell’s entire length.

HABITAT AND DISTRIBUTION

Freshwater ponds, lakes and slow-flowing, muddy-bottomed rivers. Native to Europe and Asia.

FOOD AND HABITS

Feeds on detritus and algae attached to water plants or stones. Like the other snails described here, a pulmonate (belonging to a terrestrial snail group that has adopted an aquatic life), able to breathe atmospheric air by means of a ‘lung’. All pulmonate snails are hermaphrodite and capable of laying eggs.

Moss Bladder Snail

Aplxa hypnorum

SIZE AND DESCRIPTION

Shell length to 1.3cm. Translucent, pale brown, thin and shiny shell that is sinistral, or left-handed, and elongated with a narrow aperture. Soft parts are black or dark grey, contrasting with the shell.

HABITAT AND DISTRIBUTION

Ponds and ditches, especially those that dry out periodically, in northern and central Europe.

FOOD AND HABITS

Feeds on detritus. Adult snails die when a temporary pond dries out, but the eggs are very resistant to drying out.

Orb-shell Cockle

Sphaerium corneum

SIZE AND DESCRIPTION

Length to 1.1cm. Very small freshwater clam. Small, round, lustrous yellowish-brown shell. Several species in Europe; this is one of the largest.

HABITAT AND DISTRIBUTION

Common in ponds and streams. Widespread in Britain and other parts of northern and central Europe.

FOOD AND HABITS

Suspension feeder, filtering food particles from the water, which is drawn in and expelled through two siphons. Young individuals can climb quickly through vegetation, while older ones tend to burrow in the mud or sand at the bottom. Hermaphrodite, producing about six fully developed young at a time. Life-span of about three years.

Swan Mussel

Anodonta cygnea

SIZE AND DESCRIPTION

Shell length to 23cm. The largest bivalve in British waters. Yellowish-green to olive-brown shell, elongated oval in shape with a sharply angled posterior end. Surface is marked by distinct growth lines.

HABITAT AND DISTRIBUTION

Common in large, mud-bottomed ponds, lakes, canals and slow-flowing rivers.

FOOD AND HABITS

Front part of the shell normally lies buried, but the siphons at the posterior end are always exposed. They are used by the mussel to breathe, and to feed on small animals and algae. Long lifespan of 11 years or more.

Painter’s Mussel

Unio pictorum

SIZE AND DESCRIPTION

Shell length to 10cm. Shell is buff or light brown.

HABITAT AND DISTRIBUTION

Large, mud-bottomed ponds, lakes, canals and rivers in northern and central Europe.

FOOD AND HABITS

Filter feeder, using two siphons to suck in food particles and oxygen in water, and to expel waste materials. The shell is normally partly buried, with the siphons exposed. It was historically used as a conveniently sized and shaped receptacle for holding artist’s paint. Life-span of 10 years or more. The concentric lines on the shells of mussels can be used to determine the ages of the animals.