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Encyclopedia > Mollusk
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Mollusks
Caribbean Reef Squid, Sepioteuthis sepioidea
Caribbean Reef Squid, Sepioteuthis sepioidea
Scientific classification
Kingdom: Animalia
Phylum: Mollusca
Linnaeus, 1758
Caudofoveata
Aplacophora
Polyplacophora
Monoplacophora
Bivalvia
Scaphopoda
Gastropoda
Cephalopoda
Rostroconchia

The mollusks or molluscs are the large and diverse phylum Mollusca, which includes a variety of familiar creatures well-known for their decorative shells or as seafood. These range from tiny snails, clams, and abalone to the octopus, cuttlefish and squid (which are considered the most intelligent invertebrates). There are some 70,000 described species within this phylum [1]. Download high resolution version (800x605, 283 KB)Caribbean Reef Squid Photographed by Jan Derk in March 2005 on Bonaire. ... Scientific classification or biological classification is how biologists group and categorize extinct and living species of organisms (as opposed to folk taxonomy). ... Binomial name Aptenodytes forsteri Gray, 1844 For other uses, see Animal (disambiguation). ... Carolus Linnaeus Carl Linnaeus, also known after his ennoblement as (help· info), and in English usually under the Latinized name Carolus Linnaeus (May 23, 1707 – January 10, 1778), the name with which his publications were signed, was a Swedish botanist and physician who laid the foundations for the modern scheme... Scientific classification or biological classification refers to how biologists group and categorize extinct and living species of organisms. ... Families Chaetodermatidae Limifossoridae Prochaetodermatidae Caudofoveata is a small class of the phylum mollusca, also known as Chaetodermomorpha. ... Subclasses and families Subclass Chaetodermomorpha (Caudofoveata) Family Chaetodermidae Family Falcidentidae Family Limifossoridae Family Metachaetodermatidae Family Prochaetodermatidae Family Scutopidae Subclass Neomeniomorpha (Solenogastres) Family Acanthomeniidae Family Amphimeniidae Family Dondersiidae Family Drepanomeniidae Family Epimeniidae Family Gymnomeniidae Family Hemimeniidae Family Heteroherpiidae Family Imeroherpiidae Family Lepidomeniidae Family Macellomeniidae Family Meiomeniidae Family Neomeniidae Family Perimeniidae Family... Lined Chiton (Tonicella lineata) Chitons, also called polyplacophorans and rarely polyplacophores, are 860 species of molluscs of the Class Polyplacophora. ... Orders Cyrtonellida 1987 Tryblidiida 1987 [Tryblidioidea] Tryblidiida 1982 [Bellerophontida] 1987 Pelagiellida 1987 Monoplacophora is a class of Mollusks thought to be extinct until 1952, when a living animal was dredged up from deep marine sediments. ... Orders Subclass Protobranchia Solemyoida Nuculoida Subclass Pteriomorphia - oysters Arcoida Mytiloida Pterioida Subclass Paleoheterodonta - mussels Trigoinoida Unionoida Subclass Heterodonta - clams, zebra mussels Veneroida Myoida Subclass Anomalosdesmata Pholadomyoida Bivalves are molluscs belonging to the class Bivalvia. ... Orders Dentaliida Gadilida The tusk shells are a class Scaphopoda of marine mollusks distinguished by curved tubular shells open at both ends, resembling a elephants tusk (thus the name). ... Subclasses Eogastropoda Orthogastropoda The gastropods, gasteropods, or univalves, are the largest and most successful class of mollusks, with 60,000-75,000 extant species known, comprising the snails and slugs as well as a vast number of marine and freshwater species. ... Orders Sepiida Sepiolida Spirulida Teuthida Octopoda Vampyromorphida Nautilida The Cephalopods (head-foot) are the mollusc class Cephalopoda characterized by bilateral body symmetry, a prominent head, and a modification of the mollusc foot into the form of arms or tentacles. ... Orders See text The Rostroconchia is a class of extinct mollusks dating from the early Cambrian to the late Permian. ... Phylum (plural: phyla) is a taxon used in the classification of animals, adopted from the Greek phylai the clan-based voting groups in Greek city-states. ... Spaghetti with seafood (Spaghetti allo scoglio). ... Garden Snail photographed in the USA. The name snail applies to most members of the molluscan class Gastropoda that have coiled shells. ... Maxima clam (Tridacna maxima) Clams are shelled marine or freshwater mollusks belonging to the class Bivalvia. ... Species Many: see text. ... Families 14 in two suborders, see text. ... Families Sepiadariidae Sepiidae Cuttlefish are animals of the order Sepiida, and are marine cephalopods, small relatives of squids and nautilus. ... Suborders Myopsina Oegopsina Squids are the large, diverse group of marine cephalopods popular as food in cuisines as widely separated as Korean and Italian. ... Invertebrate is a term coined by Jean-Baptiste Lamarck to describe any animal without a spinal column. ... In biology, a species is the basic unit of biodiversity. ...


The giant squid, which until recently had not been observed alive in its adult form is the largest invertebrate although it is likely that the Colossal Squid is even larger. The scientific study of mollusks is called malacology. Species Architeuthis dux Architeuthis hartingii? Architeuthis japonica? Architeuthis kirkii? Architeuthis martensi Architeuthis physeteris? Architeuthis sanctipauli Architeuthis stockii? Giant squid, once believed to be mythical creatures, are squid of the Architeuthidae family, represented by as many as eight species of the genus Architeuthis. ... Binomial name Mesonychoteuthis hamiltoni Robson, 1925 The Colossal Squid (Mesonychoteuthis hamiltoni) (sometimes called the Antarctic or Giant Cranch Squid) is believed to be the largest squid, and the only species of the genus Mesonychoteuthis. ...

Contents


Anatomy

Mollusks are triploblastic protostomes. The principal body cavity is a blood-filled hemocoel. It is unknown whether they have a true coelom (eucoelom); any coelomic cavities have been reduced to vestiges around the hearts, gonads, and metanephridia (kidney-like organs). The body is often divided into a head, with eyes or tentacles, a muscular foot and a visceral mass housing the organs. Triploblastic is a condition of the ovum in which there are three primary germinal layers: the ectoderm, mesoderm, and endoderm. ... Protostomes (from the Greek: first the mouth) are a taxon of animals. ... By the broadest definition, a body cavity is any fluid filled space in a multicellular organism. ... An open circulatory system is an arrangement of internal transport in which blood bathes the organs directly and there is no distinction between blood and interstitial fluid. ... By the broadest definition, a body cavity is any fluid filled space in a multicellular organism. ... The heart and lungs (from an older edition of Grays Anatomy) The heart (Latin cor) is a hollow, muscular organ in vertebrates that pumps blood through the blood vessels by repeated, rhythmic contractions, or a similar structure in annelids, mollusks, and arthropods. ... The gonad is the organ that makes gametes. ... Metanephridium (pl. ... Human kidneys viewed from behind with spine removed The kidneys are bean-shaped excretory organs in vertebrates. ... In anatomy, a viscus (plural viscera) is an internal organ of an animal, in particular an internal organ of the thorax or abdomen. ...


Mollusks have a mantle, which is a fold of the outer skin lining the shell, and a muscular foot that is used for motion. Many mollusks have their mantle produce a calcium carbonate external shell and their gill extracts oxygen from the water and disposes waste. All species of the phylum Mollusca have a complete digestive tract that starts from the mouth to the anus. Many have a feeding structure, the radula, mostly composed of chitin. Radulae are diverse within the Mollusca, ranging from structures used to scrape algae off rocks, to the harpoon-like structures of cone snails. Cephalopods (squid, octopuses, cuttlefish) also possess a chitinous beak. Unlike the closely related annelids, mollusks lack body segmentation. Calcium carbonate is a chemical compound, with chemical formula CaCO3. ... gills of a Smooth Newt Gills inside of a tuna head In aquatic organisms, gills are a respiratory organ for the extraction of oxygen from water and for the excretion of carbon dioxide. ... General Name, Symbol, Number oxygen, O, 8 Chemical series Nonmetals, chalcogens Group, Period, Block 16, 2, p Appearance colorless Atomic mass 15. ... For the Physics term GUT, please refer to Grand unification theory The gastrointestinal or digestive tract, also referred to as the GI tract or the alimentary canal or the gut, is the system of organs within multicellular animals which takes in food, digests it to extract energy and nutrients, and... Male Anatomy This article is about the bodily orifice. ... Radula is the scientific name for the toothed chitinous ribbon in the mouth of gastropods. ... Structure of chitin molecule In biology, chitin (pronounced keye-tin) is one of the main components in the cell walls of fungi, the exoskeletons of insects and other arthropods, and in some other animals. ... A seaweed (Laurencia) up close: the branches are multicellular and only about 1 mm thick. ... Genera Asprella Chelyconus Conus Floraconus Leptoconus The cone snails or cone shells (Conidae) are marine snails found in coral reefs. ... Orders Sepiida Sepiolida Spirulida Teuthida Octopoda Vampyromorphida Nautilida The Cephalopods (head-foot) are the mollusc class Cephalopoda characterized by bilateral body symmetry, a prominent head, and a modification of the mollusc foot into the form of arms or tentacles. ... Suborders Myopsina Oegopsina Squids are the large, diverse group of marine cephalopods popular as food in cuisines as widely separated as Korean and Italian. ... Families 14 in two suborders, see text. ... Families Sepiadariidae Sepiidae Cuttlefish are animals of the order Sepiida, and are marine cephalopods, small relatives of squids and nautilus. ... Classes and subclasses Class Polychaeta      (paraphyletic?) Class Clitellata    Oligochaeta-      (Earthworms, etc. ...


Development passes through one or two trochophore stages, one of which (the veliger) is unique to the group. These suggest a close relationship between the mollusks and various other protostomes, notably the Annelids. A trochophore (or trocophore) is a type of larva with several bands of cilia. ... The free-swimming larva of certain marine gastropods. ... Classes and subclasses Class Polychaeta      (paraphyletic?) Class Clitellata    Oligochaeta-      (Earthworms, etc. ...


Mollusk fossils are some of the best known and are found from the Cambrian onwards. The Cambrian is a major division of the geologic timescale that begins about 542 Ma (million years ago) at the end of the Proterozoic eon and ended about 488. ...


Classification

There are nine classes of mollusks, eight still living and one known only from fossils, These classes make up the 250,000 and more species of mollusk: Scientific classification or biological classification refers to how biologists group and categorize extinct and living species of organisms. ...

                 Caudofoveata (?)
                 Aplacophora
hypothetical                     Polyplacophora
ancestral                Monoplacophora
mollusk                   Gastropoda
                    Cephalopoda
                    Bivalvia
                    Scaphopoda

Brusca & Brusca (1990) suggest that the bivalves and scaphopods are sister groups, as are the gastropods and cephalopods, so indicated in the relationship diagram above. Families Chaetodermatidae Limifossoridae Prochaetodermatidae Caudofoveata is a small class of the phylum mollusca, also known as Chaetodermomorpha. ... Subclasses and families Subclass Chaetodermomorpha (Caudofoveata) Family Chaetodermidae Family Falcidentidae Family Limifossoridae Family Metachaetodermatidae Family Prochaetodermatidae Family Scutopidae Subclass Neomeniomorpha (Solenogastres) Family Acanthomeniidae Family Amphimeniidae Family Dondersiidae Family Drepanomeniidae Family Epimeniidae Family Gymnomeniidae Family Hemimeniidae Family Heteroherpiidae Family Imeroherpiidae Family Lepidomeniidae Family Macellomeniidae Family Meiomeniidae Family Neomeniidae Family Perimeniidae Family... Lined Chiton (Tonicella lineata) Chitons, also called polyplacophorans and rarely polyplacophores, are 860 species of molluscs of the Class Polyplacophora. ... Orders Cyrtonellida 1987 Tryblidiida 1987 [Tryblidioidea] Tryblidiida 1982 [Bellerophontida] 1987 Pelagiellida 1987 Monoplacophora is a class of Mollusks thought to be extinct until 1952, when a living animal was dredged up from deep marine sediments. ... Orders Subclass Protobranchia Solemyoida Nuculoida Subclass Pteriomorphia - oysters Arcoida Mytiloida Pterioida Subclass Paleoheterodonta - mussels Trigoinoida Unionoida Subclass Heterodonta - clams, zebra mussels Veneroida Myoida Subclass Anomalosdesmata Pholadomyoida Bivalves are molluscs belonging to the class Bivalvia. ... Maxima clam (Tridacna maxima) Clams are shelled marine or freshwater mollusks belonging to the class Bivalvia. ... Crassostrea gigas, Marennes-Oléron Crassostrea gigas, Marennes-Oléron Crassostrea gigas, Marennes-Oléron, opened The name oyster is used for a number of different groups of mollusks which grow for the most part in marine or brackish water. ... Genera See text. ... Orders A mussel is a bivalve mollusc that can be found in lakes, rivers, creeks, intertidal areas, and throughout the ocean. ... Orders Dentaliida Gadilida The tusk shells are a class Scaphopoda of marine mollusks distinguished by curved tubular shells open at both ends, resembling a elephants tusk (thus the name). ... Subclasses Eogastropoda Orthogastropoda The gastropods, gasteropods, or univalves, are the largest and most successful class of mollusks, with 60,000-75,000 extant species known, comprising the snails and slugs as well as a vast number of marine and freshwater species. ... Infraorders See text. ... Garden Snail photographed in the USA. The name snail applies to most members of the molluscan class Gastropoda that have coiled shells. ... SLUG is an acronym for S* Linux Users Group, where S* stands for any word starting with an S like Speed, Sleepless, Super, Satanic, Sexy, Sacred, Simbiotic, Special, Senior, Socket, Simple, and so forth. ... Genera Acmaea Bathyacmaea Lottia Notoacmea Pectinodonta Problacmaea Limpets are marine mollusks in the family Acmaeidae with flattened, cone-shaped shells. ... Families Superfamily Akeroidea Akeridae Superfamily Aplysioidea Aplysiidae Sea hares (also called sea slugs) are small marine gastropod molluscs of the suborder Anaspidea (P. Fisher, 1883) in the subclass Orthogastropoda, class Gastropoda, phylum Mollusca. ... Families Clionidae Cliopsidae Hermaeidae Hydromylidae Laginiopsidae Notobranchaeidae Pneumodermatidae Thliptodontidae Sea angels are small pteropod mollusks of the suborder Gymnosomata. ... Families Limacinidae Cavoliniidae Clioidae Creseidae Cuvierinidae Praecuvierinidae Peraclididae Cymbuliidae Desmopteridae Sea butterflies, or flapping snails, are holoplanktonic mollusks (Mollusca, Gasteropoda), belonging to the suborder Thecosomata (Blainville, 1824). ... Genera Alliodoris Anisodoris Archidoris Artachaea Austrodoris Doridium Doris Siraius The Sea Lemon is a large (up to 20 cm) flattened oval marine nudibranch without a shell. ... Orders Sepiida Sepiolida Spirulida Teuthida Octopoda Vampyromorphida Nautilida The Cephalopods (head-foot) are the mollusk class Cephalopoda characterized by bilateral body symmetry, a prominent head, and a modification of the mollusk foot, a muscular hydrostat, into the form of arms or tentacles. ... Suborders Myopsina Oegopsina Squids are the large, diverse group of marine cephalopods popular as food in cuisines as widely separated as Korean and Italian. ... Families 14 in two suborders, see text. ... Genera and species Genus Allonautilus Ward & Saunders, 1997   Allonautilus perforatus   Allonautilus scrobiculatus Genus Nautilus Linnaeus, 1758   Nautilus belauensis   Nautilus macromphalus   Nautilus pompilius pompilius   Nautilus pompilius suluensis   Nautilus stenomphalus The nautilus is a marine creature of the class Cephalopoda. ... Families Sepiadariidae Sepiidae Cuttlefish are animals of the order Sepiida, and are marine cephalopods, small relatives of squids and nautilus. ... Orders See text The Rostroconchia is a class of extinct mollusks dating from the early Cambrian to the late Permian. ...


In this phylum's level of organization, organ systems from all three primary germ layers can be found: It has been suggested that organogenesis be merged into this article or section. ...

  1. Nervous System (with brain).
  2. Excretory System (nephridium or nephridia).
  3. Circulatory System (open circulatory system).
  4. Respiratory System (gills or lungs).

All major molluscan groups possess a skeleton, though it has been lost evolutionarily in some members of the phylum. It is probable that the pre-Cambrian ancestor of the mollusks had calcium carbonate spicules embedded in its mantle and outer tissues, as is the case in some modern members. The skeleton, if present, is primarily external and composed of calcium carbonate (aragonite or calcite). The snail or gastropod shell is perhaps the most well known molluscan shell, but many pulmonate and opistrobranch snails have internalized or altogether lost the shell secondarily. The bivalve or clam shell consists of two pieces (valves), articulated by muscles and an elastic hinge. The cephalopod shell was ancestrally external and chambered, as exemplified by the ammonites and nautiloids, and still possessed by Nautilus today. Other cephalopods, such as cuttlefish, have internalized the shell, the squid have mostly organic chitinous internal shells, and the octopods have lost the shell altogether. Nephridia are invertebrate organs which function similarly to kidneys. ... gills of a Smooth Newt Gills inside of a tuna head In aquatic organisms, gills are a respiratory organ for the extraction of oxygen from water and for the excretion of carbon dioxide. ... The lungs flank the heart and great vessels in the chest cavity. ... The Precambrian or Cryptozoic is the period of the geologic timescale from the formation of Earth around 4500 million years before the present (BP) to the evolution of abundant macroscopic hard-shelled fossils, which marked the beginning of the Cambrian, some 542 million years BP. Remarkably little is known about...


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References

  • Brusca & Brusca (1990). Invertebrates, Sunderland, Mass.: Sinauer Associates, Inc..
  • Starr & Taggart (2002). Biology: The Unity and Diversity of Life, Pacific Grove, California: Thomson Learning, Inc..

External links


  Results from FactBites:
 
Mollusk - MSN Encarta (763 words)
Mollusks are highly successful in terms of ecology and adaptation, with representatives in virtually all habitats, but they are most diverse in the sea.
Although few features are common to all mollusks, the animals are not readily mistaken for anything else, and all may be treated as variants on a common theme (not to be confused with a common ancestor).
In most mollusks a larval stage follows, in which the larvae swim about for a while and then settle on the bottom and mature; this stage is often modified or absent, however.
Mollusk - Wikipedia, the free encyclopedia (705 words)
The mollusks or molluscs are the large and diverse phylum Mollusca, which includes a variety of familiar creatures well-known for their decorative shells or as seafood.
Mollusks have a mantle, which is a fold of the outer skin lining the shell, and a muscular foot that is used for motion.
It is probable that the pre-Cambrian ancestor of the mollusks had calcium carbonate spicules embedded in its mantle and outer tissues, as is the case in some modern members.
  More results at FactBites »

 
 

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