Mollusk, also spelled mollusc, any delicate-bodied invertebrate from the phylum Mollusca, usually wholly or partly enclosed in a calcium carbonate shell secreted by a soft mantle covering the human body. Together with the insects and vertebrates, it can be Probably the most diverse teams within the animal kingdom, with just about 100,000 (probably as several as one hundred fifty,000) explained species. Each and every group contains an ecologically and structurally immense assortment of types: the shell-fewer Caudofoveata; the slim-footed gliders (Solenogastres); the serially valved chitons (Placophora or Polyplacophora); the cap-shaped neopilinids (Monoplacophora); the limpets, snails, and slugs (Gastropoda); the clams, mussels, scallops, oysters, shipworms, and cockles (Bivalvia); the tubiform to barrel-formed tusk shells (Scaphopoda); as well as nautiluses, cuttlefishes, squids, and octopuses (Cephalopoda).
Dimension assortment and variety of structure
Normal molluscan capabilities have already been significantly altered, or maybe shed, in several subgroups. Among the cephalopods the giant squids (Architeuthis), the largest residing invertebrates, achieve a overall body length of 8 metres (over 26 ft); Together with the tentacle arms prolonged, the full length reaches to 22 metres. Other cephalopods exceed a length of 1 metre. Many of the remaining molluscan lessons present a significant variation in dimension: between bivalves the large clam (Tridacna) ranges nearly a hundred thirty five centimetres (four ft) and also the pen shell (Pinna) from forty to 80 centimetres; amid Mollusk gastropods the sea hares (Aplysia) expand from forty to one hundred centimetres plus the Australian trumpet, or baler (Syrinx), around sixty centimetres; between placophores the gumshoe, or gumboot chiton (Cryptochiton), achieves a length nearly thirty to forty three centimetres; and, among solenogasters, Epimenia reaches a length of 15 to 30 centimetres. Lastly, gastropods on the family Entoconchidae, which can be parasitic in echinoderm sea cucumbers, may possibly attain a size of almost 1.three metres. In contrast, You can also find moment users, under a person millimetre (0.04 inch) in size, Among the many solenogasters and gastropods.
Distribution and abundance
The mollusks have adapted to all habitats apart from air. Whilst in essence maritime, bivalves and gastropods consist of freshwater species. Gastropods have also adapted to land, with 1000s of species living a completely terrestrial existence. Observed on rocky, sandy, and muddy substrata, mollusks burrow, crawl, grow to be cemented to the surface area, or are cost-free-swimming.
Mollusks are found globally, but there is a preponderance of some groups in particular parts of the world. The near association of many molluscan groups with their foodstuff supply—regardless of whether by direct dependence on a certain food stuff supply (e.g., plant-having, or herbivores) or by involvement in foodstuff chains—restrictions their geographic distribution; one example is, bivalves on the family Teredinidae (shipworms) are associated with Wooden. Generally speaking, cold-water locations assist fewer species.
Great importance to human beings
Mollusks are of basic importance inside food items chains and as users of ecosystems. Specific species are of immediate or indirect commercial and in some cases medical great importance to individuals. Quite a few gastropod species, such as, are vital intermediate hosts for parasitic flatworms (class Trematoda, phylum Platyhelminthes), including the species that trigger schistosomiasis in human beings. Most bivalves lead to the organic and natural turnover during the intertidal (littoral) zones of marine and contemporary water simply because, as filter feeders, they filter nearly forty litres (ten gallons) of drinking water for each hour. This filtering action, nevertheless, might also severely interfere with the assorted populations of invertebrate larvae (plankton) identified suspended and absolutely free-swimming in the water. One species, the zebra mussel (Dreissena polymorpha), is considered a very harmful unique invader. Carried from Europe in ship ballast drinking water, zebra mussels were taken to the Great Lakes in 1986. So far, they have got brought on millions of dollars in professional destruction by clogging the water pipes of electrical power plants and cooling methods. These are driving several native freshwater bivalve species to extinction.Several gastropods, bivalves, and cephalopods can be a source of foods For a lot of cultures and for that reason Participate in an important function during the fishing industries of many international locations. Lots of shell-bearing molluscan species will also be utilized to fabricate ornaments and so are harvested with the pearl and mother-of-pearl industries