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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

Love Dart

A love dart is a hard, long, sharp, calcareous or chitinous dart which some hermaphroditic land snails and slugs create. Love darts are made in sexually mature animals only, and are used as part of the sequence of events during courtship before actual mating takes place. Darts are quite large compared to the size of the animal: in the case of the semi slug genus Parmarion, the length of a dart may be up to one fifth that of the semi slug's foot. Prior to copulation, each of the two snails (or slugs) attempt to "shoot" one or more darts into the other snail (or slug). There is no organ to receive the dart; this action is more analogous to a stabbing, or to being shot with an arrow. The dart does not fly through the air to reach its target however; instead it is fired as a contact shot. The love dart is emphatically not a penial stylet (in other words this is not an accessory organ for sperm transfer). The exchange of sperm between both of the two land snails is a complet...
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