Shining ram's-horn snail (Segmentina nitida)
| Kingdom | Animalia |
|---|---|
| Phylum | Mollusca |
| Class | Gastropoda |
| Order | Lymnophila |
| Family | Planorbidae |
| Genus | Segmentina (1) |
| Size | Height: 2 mm (2) Breadth: 5-6 mm (2) |
Listed as Endangered on the GB Red List (RDB1) (3).
The shining ram's-horn snail has a smooth, glossy and iridescent shell (4), measuring up to 6mm across (2), with no more than 5 whorls. The outermost whorl (body whorl) is expanded and overlaps most of the others (4), with a heart shaped aperture(4).
This snail is found throughout Europe, reaching as far north as Scandinavia. In the UK it has undergone a severe decline and is now restricted to the Norfolk Broads, parts of the Kentish Stour marshes (5), and Pevensey Levels after formerly being fairly widespread throughout much of England and known from around 90 sites (3).
Inhabits ponds and drains of grazing marshes with unpolluted, often calcareous water, preferentially choked with a rich aquatic flora in an advanced stage of plant succession(5).
Little is known of the biology of this species.
Although the precise causes of the decline of this species are not understood, the main threats are likely to be eutrophication resulting from fertiliser run-off, ditch clearance, and conversion of grazing land to arable, and the resulting reduction in the water table (3).
The Species Action Plan produced under the UK Biodiversity Action Plan (UK BAP) for the shining ram's-horn snail aims to promote the increase and expansion of existing populations and promote research into the ecology of the species (3).
Information authenticated by Shelagh Wilson of the Environment Agency.
http://www.environment-agency.gov.uk/
- Aperture: opening in the end or area of a mollusc shell out of which soft, internal body parts may emerge.
- Calcareous: containing free calcium carbonate, chalky.
- Eutrophication: nutrient enrichment of aquatic or terrestrial ecosystems.
- Succession: the progressive sequence of changes in vegetation types and animal life within a community that, if allowed to continue, result in the formation of a 'climax community' (the last stage in a succession where the vegetation reaches equilibrium with the environment).
- Whorls: in animals, the spiral or convolutions in the shell of a snail. In plants, a set of leaves, flowers, or branches that spring from a stem at the same point and encircle it.
- University of Michigan. Animal Diversity Web. (January 2002): http://animaldiversity.ummz.umich.edu/mollusca/gastropoda/lymnophila.html
- Wilson, S. (2002) Pers. Comm.
- UK BAP (January 2002): http://www.ukbap.org.uk
- The Environment Agency. (1998) Species Awareness leaflet: Snails. The Environment Agency, Bristol.
- A survey of the East Kent grazing marshes for the freshwater snail Segmentina nitida English Nature Research Report number 356, 2000.