Morphology and Behavior
Like other pulmonate land gastropods, the majority of slugs have two pairs of 'feelers' or tentacles on their head. The upper pair is light sensing and has eyespots at the ends, while 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. On one side (almost always the right hand side) of the mantle is a respiratory opening, which is easy to see when open, but difficult to see when closed. This opening is known as the pneumostome. Within the tissue of the mantle in some species is a very small, rather flat shell, or in some other cases a collection of calcareous granules.
Like most other gastropods, a slug moves by rhythmic waves of muscular contraction on the underside of its foot. It simultaneously secretes a layer of mucus on which it travels, which helps prevent damage to the foot tissues. Around the edge of the foot is the 'foot fringe' or 'skirt'.
Some slug species hibernate underground during the winter in temperate climates, but in other species, the adults die in the autumn.
Read more about this topic: Slug
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