Mud snail Bithynia tentaculata Showing the operculum
Read about the general biology of gastropods in our introductory page here
. Pond snails graze on algae and eat dead plant and animal material in the pond using their radula
. Lymnaea stagnalis
is often seen at the top of the pond, feeding upside-down on material trapped at the surface meniscus.
Freshwater snails can remain active all year round but retreat into the lower depths of a pond during the winter months. Like land snails, pond snails produce a slimy mucus from their bodies which helps to lubricate their movement over objects in the pond, but in much smaller quanities.
Snail shells are made primarily of calcium carbonate, so there is likely to be a greater diversity of pond snails in lime-rich waters, and pond molluscs may be absent in pools with very acidic water.
Freshwater snails are hermaphrodite animals that pair up to mate and exchange semen. Eggs are laid in tubes or blobs of jelly attached to plants or the sides of ponds. The eggs hatch into small versions of the adult animal.
Role of pond snails in gardens
Freshwater snails are mainly scavengers that feed on algae, plant debris and other detritus in ponds and are part of a healthy pond ecosystem Pond snails are sometimes sold as a means of reducing excessive algal growth in ponds, but it is unlikely that they are of much benefit in this respect. Algal blooms are due to a combination of nutrient-rich water and warm temperatures. When these conditions occur, algae will grow much faster than pond snails are able to eat them.
1. Anderson, R. 2005, An Annotated List of the Non-Marine Mollusca of Britain and Ireland, Journal of Conchology, London, 38:607-638.
Other sources of information
Fitter, R. and Manuel, R. 1986 Collins Field Guide ro Freshwater Life William Collins and Sons
Dobson, M. et al (2012) Guide to freshwater invertebrates. Freshwater Biological Association Publication #68
Olsen , L-H. et al (2001) Small Freshwater Creatures. Oxford University Press
of the Conchological Society of Great Britain and Ireland
Page drafted by Andrew Halstead, reviewed by Andrew Salisbury, extended and compiled by Steve Head