Great pond snail (Lymnaea stagnalis)
|Size||Shell height: 4.5 - 6 cm (2)|
Shell width: 2 - 3 cm (2)
The great pond snail is classified as Least Concern (LC) on the IUCN Red List (1). It is common and widespread in England, but is scarce in Scotland and Wales (2).
The aptly named great pond snail (Lymnaea stagnalis) is the largest pond snail in Britain (1). The great pond snail has a shiny yellowish brown shell, with a tall, slender and pointed spire (2). The shell walls are delicate and fairly transparent; they have fine markings, more prominent growth lines and variable dents on the surface (2). The great pond snail's body is yellowish grey in colour, with a large head and long, flattened tentacles (3).
The great pond snail occurs throughout Europe, northern Asia and North America (2), a distribution which is likely to have been affected by the introduction of this species to garden ponds (1).
The great pond snail is found in still or slow-moving waters where there is plenty of aquatic vegetation (2). As the specific part of the Latin name, stagnalis, suggests, this species prefers stagnant water (6).
Using its rasping tongue, known as a radula, the great pond snail feeds on both plant and animal matter, leaving behind distinctive feeding marks (7). It can even attack newts, small fishes, and water beetle larvae and may occasionally be cannibalistic, eating smaller great pond snails (3).
The great pond snail lays large gelatinous egg-masses on weeds and other objects in the pond (6). These egg masses measure between five and six centimetres in length (5), and can contain as many as 50 to 120 eggs (6). The size to which a specimen will grow is dependent upon the volume of water in the pond; individuals grow larger in big ponds. Young specimens are slender and have more translucent shells than mature snails (6).
Although the great pond snail often comes to the surface to take in air into a respiratory cavity, when the pond becomes covered in ice or when the snail moves to deeper water in winter, it is able to take in oxygen from the water through the skin. The wide tentacles play a key role in the intake of oxygen; the surface of the tentacles is covered in tiny hair-like structures known as 'cilia' which function to increase their surface area, thus increasing the intake of air (4).
The great pond snail is not currently threatened.
No conservation action has been targeted at the great pond snail.
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- Larvae: stage in an animal's lifecycle after it hatches from the egg. Larvae are typically very different in appearance to adults; they are able to feed and move around but usually are unable to reproduce.
- Radula: in some molluscs, a narrow structure that bears teeth and is used to rasp at food.
IUCN Red List (April, 2011)
- Pfleger, V. and Chatfield, J. (1983) A Guide to Snails of Britain and Europe. The Hamlyn Publishing Group Ltd., London.
- Step. E. (1951) Shell Life: an Introduction to the British Mollusca. Frederick Warne & Co. Ltd., London.
- Nichols, D., Cooke, J. and Whiteley, D. (1971) The Oxford Book of Invertebrates. Oxford University Press, Oxford
- Sterry, P. (1997) Complete British Wildlife Photo Guide. Harper Collins Publishers, Ltd., London.
- Olsen, L., Sunesen, J. and Pedersen, B. (2001) Small Freshwater Creatures. Oxford University Press, Oxford.
- Janus, H. (1982) The Illustrated Guide to Molluscs. Harold Starke Ltd., London.