Of remarkable size, its elegant shell rolled up into a long point, the great snail crisscrosses the ponds with its quiet glide.
An aquatic snail
The great snail, Limnaea stagnalis, is a snail, with lungs, installed in quiet waters, with slow or non-existent currents. Imposing gastropod, its size can reach 5 to 6 cm, it remains elegant with its lengthened shell with the many spires. Accustomed to ponds, it is found throughout Europe, in the Northern hemisphere, Asia and America, alongside other limneas, all of the family Lymnaeidae.
A siphon to breathe oxygen from the air
If it lives in water, the Great Limnea cannot breathe oxygen. Its lungs need air. The attentive observer will have to wait long moments to see it finally going back to the surface, deploying a siphon, piercing the surface of the water and capturing the air necessary for long immersions. Immersions all the more long as the water will be well oxygenated, the gas exchanges taking place then also by the skin.
Its house on the back
Classic snail, the big Limnée carries its house. A "coat" on its back secretes a calcareous formation, of only one part it manufactures a twisted shell. In which she shelters her soft mollusc body, in case of predation and in times of drought. If its waiting in its shell must be prolonged, it will close the "door" using dried mucus, burying itself if possible in the mud.
A quiet path
On its muscular oval foot, the large Limnea surveys the bottom of the pond, its reliefs, slips from plants to plants. One can see it floating sometimes, between two waters, in ascending or descending movement. At the surface of the pond, between water and air, it is placed upside down and its mucus-covered foot is flush with the air. She glides slowly, feeding on the biofilm formed on the stagnant water.
She grazes, grazes
The great dabbler spends long moments grazing. Its two long triangular tentacles are surmounted by two eyes, below which is placed the mouth. In this mouth is the radula, which could resemble a rasping tongue, covered with asperities that allow it to scrape decomposing plants, to graze the aquatic bottom, to tear some particles from occasional decomposing corpses.
Males and females, aquatic meetings
The great snail, like many snails, is hermaphroditic, the same individual carrying, in a complex anatomy, the male and female sexes. After cross fertilization, sometimes with several individuals, the eggs are laid on the walls or on the plants in extremely adhesive elongated socks. After three weeks, more or less according to the temperature, the eggs hatch and come out tiny Limnea whose body and shell will grow in a few months.
Majestic, slow-moving, the great snail is one of the easiest to observe in the pond. Not very demanding, an abundant vegetation, a calm water and detritus will be enough to welcome it.
