Snail shell7/28/2023 ![]() ![]() It seems to have been affected by air pollution and soil acidification in some parts of England. It is not found in the Hebrides, Orkney or Shetland. nemoralis is rare and scattered in northern Scotland, where it has been introduced. In Slovakia it was still known only from a single garden centre by 2020. in Poland, Latvia, Estonia, southern Finland, the east coast of Sweden) but also now elsewhere in Poland, and in Ukraine, Belarus and Russia. In Central and Eastern Europe it has spread particularly along the Baltic coast (e.g. Thus it is known from most of the Iberian Peninsula, France, Great Britain, Ireland, Belgium, the Netherlands, Germany, Denmark, southern Sweden and Norway, Switzerland, Austria, the Czech Republic, Hungary, Bosnia, Croatia, and the northern half of Italy. nemoralis is from Western and Northern Europe to Central Europe, but it has been spreading eastwards especially over the last few decades. Most probably, the polymorphism has multiple causes. Natural selection would then favour a diversity of colours and patterns as an antipredator adaptation. ![]() Balanced polymorphism could arise when a predator like the song thrush develops a 'search image' for the commonest morph, so that the rarer morphs are less likely to be predated. Researchers have variously argued that the cause is random genetic drift and founder effects, different selection pressures in different areas with mixing by migration, and balanced polymorphism. Īnother question is why the variation persists, usually even within a locality. Climatic selection can also explain why yellow shells are commoner in the south. The explanation might be camouflage or climatic selection: paler, more reflective colours in sunny environments reduce water loss and overheating. For instance, in stable habitats shells tend to be darker in woodland than in open habitats. The polymorphism has also been intensely studied for its evolution and ecology. The genetics underlying this variation is extensively understood and is shared with C. The bands vary in intensity of colour, in width and in number, from zero to five. Additionally the shells can be with or without dark bands. The background colour of the shell various along a continuum from brown through pink to yellow and sometimes almost white. Main article: Cepaea: the shell polymorphismĬepaea nemoralis is highly polymorphic in shell colour and banding. nemoralis consistently has a dark-brown lip to its shell, whilst C. Cepaea nemoralis tends to grow larger, but usually the species can most easily be recognised by the colour of the lip of adult shells. They share much the same habitat and exhibit a similar range of shell colours and banding patterns. Identification Ĭepaea nemoralis is closely related to Cepaea hortensis. An adult shell consists of 4½–5½ whorls, with a width of 18–25 mm and a height of 12–22 mm. The umbilicus is closed in adults but narrowly open in juveniles. The thickened and slightly out-turned apertural lip of adults is usually dark brown, but can be white in some regions. Names for many colour variants were coined in the nineteenth century but this system has been replaced by an independent scoring of shell colour and the presence/absence and fusion of individual bands numbered 1 to 5. The colour of the shell is highly variable it ranges from brown, through pink, to yellow or even whitish, with or without one to five dark-brown bands. Description Ĭepaea nemoralis is among the largest and, because of its bright colouration, one of the best-known snails in Western Europe. It is used as a model organism in ecological genetics, including in citizen science projects. Cepaea nemoralis nemoralis (Linnaeus, 1758)Ĭepaea nemoralis is the type species of the genus Cepaea.Cepaea nemoralis etrusca (Rossmässler, 1835).It is one of the commonest large species of land snail in Europe, and has been introduced to North America. The grove snail, brown-lipped snail or lemon snail ( Cepaea nemoralis) is a species of air-breathing land snail, a terrestrial pulmonate gastropod mollusc. Cepaea (Cepaea) nemoralis (Linnaeus, 1758). ![]()
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