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A slug on a wall in Kanagawa, Japan.. Slug, or land slug, is a common name for any apparently shell-less terrestrial gastropod mollusc.The word slug is also often used as part of the common name of any gastropod mollusc that has no shell, a very reduced shell, or only a small internal shell, particularly sea slugs and semi-slugs (this is in contrast to the common name snail, which applies to ...
Molluscs are a large phylum of invertebrate animals, many of which have shells. Edible molluscs are harvested from saltwater, freshwater, and the land, and include numerous members of the classes Gastropoda (snails), Bivalvia (clams, scallops, oysters etc.), Cephalopoda (octopus and squid), and Polyplacophora (chitons).
In contrast to all other molluscan classes, the Aplacophora have no shell, and are instead covered by aragonitic sclerites (calcareous spicules), which can be solid or hollow. These spicules can be arranged perpendicular to one another within the cuticle to form a skeleton, or can stick up to form a palisade, or can lie flat against the cuticle.
The mollusc (or mollusk [spelling 1]) shell is typically a calcareous exoskeleton which encloses, supports and protects the soft parts of an animal in the phylum Mollusca, which includes snails, clams, tusk shells, and several other classes. Not all shelled molluscs live in the sea; many live on the land and in freshwater.
The generalized mollusc is an unsegmented, bilaterally symmetrical animal and has a single, "limpet-like" shell on top. The shell is secreted by a mantle covering the upper surface. The underside consists of a single muscular "foot". [19] The visceral mass, or visceropallium, is the soft, nonmuscular metabolic region of the mollusc.
Living abalone in tank showing epipodium and tentacles, anterior end to the right. Abalone (/ ˈ æ b ə l oʊ n i / ⓘ or / ˌ æ b ə ˈ l oʊ n i /; via Spanish abulón, from Rumsen aulón) is a common name for any small to very large marine gastropod mollusc in the family Haliotidae, which once contained six genera but now contains only one genus, Haliotis. [1]
Shellfish have formed part of the human diet since prehistoric times, a fact evidenced by the remains of mollusc shells found in ancient middens. Examinations of these deposits in Peru has provided a means of dating long past El Niño events because of the disruption these caused to bivalve shell growth. [87]
A Nautilus shell from Broome, Australia. The majority of recovered shells, like this example, are found as drift shells. Many shells recovered from areas of the world have not yet been identified down to the level of species, however, are still identifiable as members of the genus Nautilus.