Lymnaea stagnalis

Origin

 * The great pond snail is a widespread species distributed in Asia (central, north and south and southeast), North America and North Africa. This species also has a widespread European distribution, occurring in all European Mediterranean countries and is introduced to New Zealand.

Sexing

 * Simultaneous hermaphrodites, self-fertilization does not occur. The great pond snail lays large gelatinous egg-masses on weeds and other objects in the tank/pond. These egg masses measure between five and six centimetres in length, and can contain as many as 50 to 120 eggs. They are cannibalistic, eating smaller great pond snails.

Tank compatibility

 * This snail will be peaceful towards all tank/pond mates, as long as they are not predatory. The great pond snails are great scavengers. Any leftover food or dead carcass will quickly be eaten by these snails. It may eat smaller snails, whose shell has approximately the same diameter as its mouth. Calcium supplementation reduces the predation on smaller snails.

Diet

 * Using its rasping tongue, known as a radula, the great pond snail feeds on both plant and animal matter, leaving behind distinctive feeding marks. It devours smaller snails whole. Like all gastropods it needs calcium supplements.

Feeding regime

 * Approximately once a week.

Environment Specifics

 * This species inhabits slow or still waters, such as the edge of pools, streams, reservoirs, amongst others where there is plenty of aquatic vegetation. They like muddy sand or crushed stone bottom.

Behaviour

 * The great pond snail can overwinter in ponds that does not freezes to the bottom. 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. It spends much time among surface vegetation, and will rest on floating plants that can supports its weight. The species can be transported by birds, in part accounting for its very wide distribution.

Identification

 * The great pond snail has a shiny yellowish brown shell, with a tall, slender and pointed spire. The shell walls are delicate and fairly transparent; they have fine markings, more prominent growth lines and variable dents on the surface. The great pond snail's body is yellowish grey in colour, with a large head and long, flattened tentacles.