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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.
Bivalvia (/ b aɪ ˈ v æ l v i ə /) or bivalves, in previous centuries referred to as the Lamellibranchiata and Pelecypoda, is a class of aquatic molluscs (marine and freshwater) that have laterally compressed soft bodies enclosed by a calcified exoskeleton consisting of a hinged pair of half-shells known as valves.
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 shell is an exoskeleton, which protects from predators, mechanical damage, and dehydration, but also serves for muscle attachment and calcium storage. Some gastropods appear shell-less ( slugs ) but may have a remnant within the mantle, or in some cases the shell is reduced such that the body cannot be retracted within it ( semi-slug ).
A bivalve shell is the enveloping exoskeleton or shell of a bivalve mollusc, composed of two hinged halves or valves. The two half-shells, called the "right valve" and "left valve", are joined by a ligament and usually articulate with one another using structures known as "teeth" which are situated along the hinge line.
Each coccolithophore is a cell surrounded by the exoskeleton coccosphere, but there exists a wide range of sizes, shapes and architectures between different cells. Advantages of these plates may include protection against infection by viruses and bacteria, as well as protection from grazing zooplankton .
These underwater mollusks have inspired scientists to make one of the strongest adhesives on the market. Researchers have cracked how mussels attach to wet surfaces, and have replicated it into an ...
Spicules are secreted by cells that do not express engrailed, but these cells are surrounded by engrailed-expressing cells. [14] These neighbouring cells secrete an organic pellicle on the outside of the developing spicule, whose aragonite is deposited by the central cell; subsequent division of this central cell allows larger spines to be ...