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November 30, 2010

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Slug

Slug is a common name that is normally applied to any gastropod mollusc that lacks a shell, has a very reduced shell, or has a small internal shell. This is in contrast to the common name snail, which is applied to gastropods that have coiled shells that are big enough to retract into. Slugs belong to several different lineages that also include snails with shells. The shell-less condition has arisen many times independently during the evolutionary past, and thus the category "slug" is emphatically a polyphyletic one. The various groups of land slugs are not closely related, despite a superficial similarity in the overall body form. As well as land slugs, there are also many marine slugs and even one freshwater slug species, but the common name "slug" is most frequently applied to air-breathing land slugs, while the marine forms are usually known as sea slugs. Land gastropods with a shell that is not quite vestigial, but is too small to retract into (like many in t...

Land snails

Land snails are usually found in shady places, such as under logs, stones or rocks. They prefer to live at the edge of ponds or rivers or in wooded areas. Most land snails live on the ground. However a few, such as the large and colourful tropical snails, are found in trees. The land snail uses a muscular organ called a foot to crawl along. The foot moves in a wave-like motion. As it is moving, the snail releases a sticky slime. This acts like a kind of oil, or lubrication, to help the snail slide over the ground. When the weather is dry, the snail locks itself into its shell with a piece of hardened slime to stop itself from

European pulmonate land snail, which has been introduced to many other countries

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