Snail Gastropoda about Slug Semilimax Oregon State University Plant Garden

>For other meanings, see Slug (disambiguation) Slugs are gastropods without shells or with very small shells (often which are internal), in contrast with snails from which they share a common ancestor, which have a prominent shell. Although they undergo torsion (180 degree twisting of internal organs) during development, their bodies are streamlined and worm-like, and so show little external evidence of it. This same basic design developed independently in several different groups, the largest being the sea slugs or nudibranchs. Other slugs are found on land, but their soft, slimy bodies are prone to desiccation, so they are confined to moist environments. Among the various species are the grey field slug, Deroceras reticulatus; the garden slug, Arion hortensis; the leopard slug, Limax maximus; and the banana slug, Ariolimax columbianus. Like snails, slugs have two pairs of 'feelers' or tentacles on their head. The upper pair--optical tentacles--are light sensors; the lower pair provides the sense of smell. Both pairs are retractable and can be regrown if lost. On top of the slug, behind the head, is the saddle-shaped mantle, and under this are the genital opening and anus. The mantle also has a hole, the pneumostome, for respiration. The slug moves by rythmic muscular action of its foot. See more at Wikipedia.org...