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The mollusc (or mollusk [a]) 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.
Mollusca is a phylum of protostomic invertebrate animals, whose members are known as molluscs or mollusks [a] (/ ˈ m ɒ l ə s k s /). Around 76,000 extant species of molluscs are recognized, making it the second-largest animal phylum after Arthropoda . [ 5 ]
The terminology used to describe the shells of gastropods includes: Aperture: the opening of the shell; Lip: peristome: the margin of the aperture; Apex: the smallest few whorls of the shell; Body whorl (or last whorl): the largest whorl in which the main part of the visceral mass of the mollusk is found
This space contains the mollusk's gills, anus, osphradium, nephridiopores, and gonopores. The mantle cavity functions as a respiratory chamber in most mollusks. In bivalves it is usually part of the feeding structure. In some mollusks the mantle cavity is a brood chamber, and in cephalopods and some bivalves such as scallops, it is a locomotory ...
Mussel (/ ˈ m ʌ s ə l /) is the common name used for members of several families of bivalve molluscs, from saltwater and freshwater habitats. These groups have in common a shell whose outline is elongated and asymmetrical compared with other edible clams, which are often more or less rounded or oval.
Its composition results in a dark colored ink, rich in ammonium salts and amino acids that may have a role in phagomimicry defenses. [31] The ink can be ejected to create a " smoke screen " to hide the cuttlefish's escape, or it can be released as a pseudomorph of similar size to the cuttlefish, acting as a decoy while the cuttlefish swims away.
In addition, the water flows through incurrent siphon ventrally and exit out of the body through excurrent dorsally to the body. The valves of the shell are made of either calcite (as with, e.g. oysters) or both calcite and aragonite , usually with the aragonite forming an inner layer, as is the case with the Pteriida which have this layer in ...
The taxonomic term Bivalvia was first used by Linnaeus in the 10th edition of his Systema Naturae in 1758 to refer to animals having shells composed of two valves. [3] More recently, the class was known as Pelecypoda, meaning "axe-foot" (based on the shape of the foot of the animal when extended).