Chitons are mollusks that live near the edge of the ocean in most of the world, but some species have been found in deep water. They creep along slowly on their muscular feet and cling to rocks. Chitons have shells made up of eight overlapping calcareous plates. Classes Caudofoveata Aplacophora Polyplacophora - Chitons Monoplacophora Bivalvia - Bivalves Scaphopoda - Tusk shells Gastropoda - Snails and Slugs Cephalopoda - Squids, Octopuses, etc. ... Calcareous formed from or containing a high proportion of Calcium carbonate. ...

Chitons are also called sea cradles, loricates, coat-of-mail shells, polyplacophorans, Chitonidae, and rarely polyplacophores. There are 900-1000 extant species of molluscs of the class Polyplacophora, which was formerly called Amphineura ^[1]). Chitons, unlike some other molluscs, are entirely marine; most species are found in the intertidal zone (the "littoral" zone), on or in rocks, but some species have been found as deep as 6000 meters (about 20,000 feet). Individual plates are sometimes called "butterfly shells." In biology, a species is one of the basic units of biodiversity. ... Classes 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. ... A littoral is the region near the shoreline of a body of fresh or salt water. ...

Structure

The underside of Cryptochiton stelleri (The gumboot chiton), showing the foot, in the center, surrounded by the gills and mantle. The mouth is visible above and to the left of the foot.

Ontogeny of Polyplacophora: First image is trochophore, second is stadium in metamorphosis, third is juvenile Polyplacophora.

The calcareous armour shell that chitons carry dorsally are protective, made wholly of aragonite, and variously colored, patterned, smooth or sculptured. The shell is divided into eight articulating plates (also called valves) embedded in the tough muscular girdle that surrounds the chiton's body. This arrangement allows chitons to roll into a protective ball when dislodged and to cling tightly to even irregular surfaces. The girdle is often ornamented with spicules, bristles, hairy tufts, spikes, or snake-like scales. The majority of the body is a snail-like foot, but no head or other soft-parts beyond the girdle are visible from the dorsal side. Between the body and the girdle, there is a mantle cavity, connected to the outside by two water channels. The one on the side is the incurrent water channel. The one attached to the anus is the excurrent water channel. [1] The gills hang down into the mantle cavity, usually near the anus. An anterior head has a mouth containing a tongue-like structure called a radula, which has numerous rows of usually 17 teeth each. The teeth are coated with magnetite, a ferric/ferrous oxide mineral that hardens the teeth. The radula is used to scrape microscopic algae off the substratum. It is also shaped kind of like a deformed ball sack. Image File history File links Cryptochiton_stelleri_underside. ... Image File history File links Cryptochiton_stelleri_underside. ... Binomial name Cryptochiton stelleri (Middendorff, 1847) The Gumboot chiton (Cryptochiton stelleri), also known as the Giant Pacific chiton, is the largest member of the chiton family, growing to 33 centimeters (13 in). ... Image File history File linksMetadata No higher resolution available. ... Image File history File linksMetadata No higher resolution available. ... trochophore A - episphere B - hyposphere 1 - ganglia 2 - apical tuft 3 - prototroch 4 - metatroch 5 - nephridium 6 - anus 7 - protonephridia 8 - gastrointestinal tract 9 - buccal opening 10 - blastocoele A trochophore (or trocophore) is a type of larva with several bands of cilia. ... Armour sucks ass alottttttttttt Armour was also commonly used to protect war animals, such as war horses and elephants. ... Various seashells Danielle A shell is the hard, rigid outer covering, or integument, allanimals. ... Aragonite Aragonite is a polymorph of the mineral calcite, both having the chemical composition CaCO3. ... The name snail applies to most members of the molluscan class Gastropoda that have coiled shells. ... For other uses, see Foot (disambiguation). ... The mantle is an organ found in mollusks. ... Impact from a water drop causes an upward rebound jet surrounded by circular capillary waves. ... In physical geography, a channel is the physical confine of a river, slough or ocean strait consisting of a bed and banks. ... Female Human Anatomy Male Human Anatomy This article is about the bodily orifice. ... 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. ... For other uses of the word head, see head (disambiguation). ... It has been suggested that this article or section be merged with mouth (human). ... Radula is the scientific name for the toothed chitinous ribbon in the mouth of gastropods. ... // Headline text Magnetite is a ferrimagnetic mineral form of iron(II,III) oxide, with chemical formula Fe3O4, one of several iron oxides and a member of the spinel group. ...

Name

A chiton shell on display (Acanthopleura spinosa).

The English name "chiton" originates from the Latin word chitōn, which means "mollusk", and in turn is derived from the Greek word "khitōn", meaning "tunic" (which also is the source of the word chitin). The Greek word "khitōn" can be traced to the Central Semitic word "*kittan", which is from the Akkadian words "kitû" or "kita’um", meaning flax or linen, and originally the Sumerian word "gada" or "gida".^[2] Image File history File linksMetadata Size of this preview: 800 × 376 pixels Full resolution (2098 × 986 pixel, file size: 506 KB, MIME type: image/jpeg) Acanthopleura spinosa, a chiton shell on display. ... Image File history File linksMetadata Size of this preview: 800 × 376 pixels Full resolution (2098 × 986 pixel, file size: 506 KB, MIME type: image/jpeg) Acanthopleura spinosa, a chiton shell on display. ... Latin was the language originally spoken in the region around Rome called Latium. ... A Danaid, wearing a low-girded chiton A chiton was a piece of clothing in the Ancient Greek world. ... Classes 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. ... A Danaid, wearing a low-girded chiton A chiton was a piece of clothing in the Ancient Greek world. ... Structure of the chitin molecule, showing two of the N-Acetylglucosamine units that repeat to form long chains in beta-1,4 linkage. ... In linguistics and ethnology, Semitic (from the Biblical Shem, Hebrew: שם, translated as name, Arabic: سام) was first used to refer to a language family of largely Middle Eastern origin, now called the Semitic languages. ... Akkadian (lišānum akkadÄ«tum) was a Semitic language (part of the greater Afro-Asiatic language family) spoken in ancient Mesopotamia, particularly by the Assyrians and Babylonians. ... Sumerian ( native tongue) was the language of ancient Sumer, spoken in Southern Mesopotamia from at least the 4th millennium BCE. It was gradually replaced by Akkadian as a spoken language in the beginning of the 2nd millenium BCE, but continued to be used as a sacred, ceremonial, literary and scientific...

The Greek-derived name Polyplacophoran comes from the words poly- (many), plako- (tablet), and -phoros (bearing).

Scientific Investigation

Chitons were first studied by Carolus Linnaeus in 1758. Since his description of the first four species, chitons have been variously classified. They were called Cyclobranchians ("round arm") in the early 19th century, and then grouped with the aplacophorans in the subphylum Amphineura in 1876. The Class Polyplacophora was named by J. E. Gray in 1821. Carl Linnaeus, Latinized as Carolus Linnaeus, also known after his ennoblement as  , (May 23, 1707[1] – January 10, 1778), was a Swedish botanist, physician and zoologist[2] who laid the foundations for the modern scheme of nomenclature. ... Alternative meaning: Nineteenth Century (periodical) (18th century — 19th century — 20th century — more centuries) As a means of recording the passage of time, the 19th century was that century which lasted from 1801-1900 in the sense of the Gregorian calendar. ... The coronation banquet for George IV 1821 was a common year starting on Monday (see link for calendar). ...

Activities

Chitons eat algae, bryozoans, diatoms and sometimes bacteria by scraping the rocky substrate with their well-developed radula. Some species have an enlarged anterior girdle by which they feed on other small invertebrates, such as shrimp and possibly even small fish, by holding the girdle up off the surface and then clamping down on the unsuspecting, shelter-seeking prey. Some chitons exhibit homing behavior, returning to the same spot during the day and coming out at night to feed. A seaweed (Laurencia) up close: the branches are multicellular and only about 1 mm thick. ... Phyla/Divisions Actinobacteria Aquificae Bacteroidetes/Chlorobi Chlamydiae/Verrucomicrobia Chloroflexi Chrysiogenetes Cyanobacteria Deferribacteres Deinococcus-Thermus Dictyoglomi Fibrobacteres/Acidobacteria Firmicutes Fusobacteria Gemmatimonadetes Nitrospirae Omnibacteria Planctomycetes Proteobacteria Spirochaetes Thermodesulfobacteria Thermomicrobia Thermotogae Bacteria (singular, bacterium) are a major group of living organisms. ...

Predators include seagulls, starfish, crab, fish, and sea anemones. Look up gull in Wiktionary, the free dictionary. ... Orders Brisingida (100 species[1]) Forcipulatida (300 species[2]) Paxillosida (255 species[3]) Notomyotida (75 species[4]) Spinulosida (120 species[5]) Valvatida (695 species[6]) Velatida (200 species[7]) For other uses, see Starfish (disambiguation). ... Superfamilies Dromiacea Homolodromioidea Dromioidea Homoloidea Eubrachyura Raninoidea Cyclodorippoidea Dorippoidea Calappoidea Leucosioidea Majoidea Hymenosomatoidea Parthenopoidea Retroplumoidea Cancroidea Portunoidea Bythograeoidea Xanthoidea Bellioidea Potamoidea Pseudothelphusoidea Gecarcinucoidea Cryptochiroidea Pinnotheroidea * Ocypodoidea * Grapsoidea * An asterisk (*) marks the crabs included in the clade Thoracotremata. ... A giant grouper at the Georgia Aquarium Fish are aquatic vertebrates that are typically cold-blooded; covered with scales, and equipped with two sets of paired fins and several unpaired fins. ... Families Many, see text. ...

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Classification

Most classification schemes in use today are based, at least in part, on Pilsbry's Manual of Conchology (1892-1894), extended and revised by Kaas and Van Belle (1985-1990).

Since chitons were first described by Linnaeus (1758) there have been extensive taxonomic studies at the species level. However, the taxonomic classification at higher levels in the group has remained somewhat unsettled.

The most recent classification (Sirenko 2006) is based not only on shell morphology, as usual, but also other important features including aesthetes, girdle, radula, gills, glands, egg hull projections and spermatozoids. It includes all the living and extinct genera of chitons.

This system is now generally accepted.

• Class Polyplacophora Gray, 1821
  • Subclass Paleoloricata Bergenhayn, 1955
    • Order Chelodida Bergenhayn, 1943
      • • Family Chelodidae Bergenhayn, 1943
          • Chelodes Davidson et King, 1874
          • Euchelodes Marek, 1962
          • Calceochiton Flower, 1968
    • Order Septemchitonida Bergenhayn, 1955
      • • Family Gotlandochitonidae Bergenhayn, 1955
          • Gotlandochiton Bergenhayn, 1955
        • Family Helminthochitonidae Van Belle, 1975
          • Kindbladochiton Van Belle, 1975
          • Diadelochiton Hoare, 2000
          • Helminthochiton Salter in Griffith et M'Coy, 1846
          • Echinochiton Pojeta, Eernisse, Hoare et Henderson, 2003
        • Family Septemchitonidae Bergenhayn, 1955
          • Septemchiton Bergenhayn, 1955
          • Paleochiton A. G. Smith, 1964
          • Thairoplax Cherns, 1998
  • Subclass Loricata Shumacher, 1817
    • Order Lepidopleurida Thiele, 1910
      • Suborder Cymatochitonina Sirenko et Starobogatov, 1977
        • Family Acutichitonidae Hoare, Mapes et Atwater, 1983
          • Acutichiton Hoare, Sturgeon et Hoare, 1972
          • Elachychiton Hoare, Sturgeon et Hoare, 1972
          • Harpidochiton Hoare et Cook, 2000
          • Arcochiton Hoare, Sturgeon et Hoare, 1972
          • Kraterochiton Hoare, 2000
          • Soleachiton Hoare, Sturgeon et Hoare, 1972
          • Asketochiton Hoare et Sabattini, 2000
        • Family Cymatochitonidae Sirenko et Starobogatov, 1977
          • Cymatochiton Dall, 1882
          • Compsochiton Hoare et Cook, 2000
        • Family Gryphochitonidae Pilsbry, 1900
          • Gryphochiton Gray, 1847
        • Family Lekiskochitonidae Smith et Hoare, 1987
          • Lekiskochiton Hoare et Smith, 1984
        • Family Permochitonidae Sirenko et Starobogatov, 1977
          • Permochiton Iredale et Hull , 1926
      • Suborder Lepidopleurina Thiell, 1910
        • Family Ferreiraellidae Dell’ Angelo et Palazzi, 1991
          • Glaphurochiton Raymond, 1910
          •  ?Pyknochiton Hoare, 2000
          •  ?Hadrochiton Hoare, 2000
          • Ferreiraella Sirenko, 1988
        • Family Glyptochitonidae Starobogatov et Sirenko, 1975
          • Glyptochiton Konninck, 1883
        • Family Leptochitonidae Dall, 1889
          • Colapterochiton Hoare et Mapes, 1985
          • Coryssochiton DeBrock, Hoare et Mapes, 1984
          • Proleptochiton Sirenko et Starobogatov, 1977
          • Schematochiton Hoare, 2002
          • Pterochiton (Carpenter MS) Dall, 1882
          • Leptochiton Gray, 1847
          • Parachiton Thiele, 1909
          • Trachypleura Jaeckel, 1900
          • Pseudoischnochiton Ashby, 1930
          • Lepidopleurus Risso, 1826
          • Hanleyella Sirenko, 1973
        • Family Camptochitonidae Sirenko, 1997
          • Camptochiton DeBrock, Hoare et Mapes, 1984
          • Pedanochiton DeBrock, Hoare et Mapes, 1984
          • Euleptochiton Hoare et Mapes, 1985
          • Pileochiton DeBrock, Hoare et Mapes, 1984
          • Chauliochiton Hoare et Smith, 1984
          • Stegochiton Hoare et Smith, 1984
        • Family Nierstraszellidae Sirenko, 1992
          • Nierstraszella Sirenko, 1992
        • Family Mesochitonidae Dell’ Angelo et Palazzi, 1989
          • Mesochiton Van Belle, 1975
          • Pterygochiton Rochebrune, 1883
        • Family Protochitonidae Ashby, 1925
          • Protochiton Ashby, 1925
          • Deshayesiella (Carpenter MS) Dall, 1879
          • Oldroydia Dall, 1894
        • Family Hanleyidae Bergenhayn, 1955
          • Hanleya Gray, 1857
    • Order Chitonida Thiele, 1910
      • Suborder Chitonina Thiele, 1910
      • Superfamily Chitonoidea Rafinesque, 1815
        • Family Ochmazochitonidae Hoare et Smith, 1984
          • Ochmazochiton Hoare et Smith, 1984
        • Family Ischnochitonidae Dall, 1889
          • Ischnochiton Gray, 1847
          • Stenochiton H. Adams et Angas, 1864
          • Stenoplax (Carpenter MS) Dall, 1879
          • Lepidozona Pilsbry, 1892
          • Stenosemus Middendorff, 1847
          • Subterenochiton Iredale et Hull, 1924.
          • Thermochiton Saito et Okutani, 1990
          • Connexochiton Kaas, 1979
          • Tonicina Thiele, 1906
        • Family Callistoplacidae Pilsbry, 1893
          • Ischnoplax Dall, 1879
          • Callistochiton (Carpenter MS) Dall, 1879
          • Callistoplax Dall, 1882
          • Ceratozona Dall, 1882
          • Calloplax Thiele, 1909
        • Family Chaetopleuridae Plate, 1899
          • Chaetopleura Shuttleworth, 1853
          • Dinoplax (Carpenter MS) Dall, 1879
        • Family Loricidae Iredall et Hull, 1923
          • Lorica H. et A. Adams, 1852
          • Loricella Pilsbry, 1893
          • Oochiton Ashby, 1929
        • Family Callochitonidae Plate, 1901
          • Callochiton Gray, 1847
          • Eudoxochiton Shuttleworth, 1853
          • Vermichiton Kaas, 1979
        • Family Chitonidae Rafinesque, 1815
          • Subfamily Chitoninae Rafinesque, 1815
          • Chiton Linnaeus, 1758
          • Radsia Gray, 1847
          • Rhyssoplax Thiele, 1893
          • Teguloaplax Iredale & Hull, 1926
          • Mucrosquama Iredale, 1893
          • Subfamily Toniciinae Pilsbry, 1893
          • Tonicia Gray, 1847
          • Onithochiton Gray, 1847
          • Subfamily Acanthopleurinae Dall, 1889
          • Acanthopleura Guilding, 1829
          • Liolophura Pilsbry, 1893
          • Enoplochiton Gray, 1847
          • Squamopleura Nierstrasz, 1905
        • Superfamily Schizochitonoidea Dall, 1889
        • Family Schizochitonidae Dall, 1889
          • Incissiochiton Van Belle, 1985
          • Schizochiton Gray, 1847
      • Suborder Acanthochitonina Bergenhayn, 1930
        • Family Mopalioidea Dall, 1889
        • Family Tonicellidae Simroth, 1894
        • Subfamily Tonicellinae Simroth, 1894
          • Lepidochitona Gray, 1821
          • Particulazona Kaas, 1993
          • Boreochiton Sars, 1878
          • Tonicella Carpenter, 1873
          • Nuttallina (Carpenter MS) Dall, 1871
          • Spongioradsia Pilsbry, 1894
          • Oligochiton Berry, 1922
        • Subfamily Juvenichitoninae Sirenko, 1975
          • Juvenichiton Sirenko, 1975
          • Micichiton Sirenko, 1975
          • Nanichiton Sirenko, 1975
        • Family Schizoplacidae Bergenhayn, 1955
          • Schizoplax Dall, 1878
        • Family Mopaliidae Dall, 1889
        • Subfamily Heterochitoninae Van Belle, 1978
          • Heterochiton Fucini, 1912
          • Allochiton Fucini, 1912
        • Subfamily Mopaliinae Dall, 1889
          • Plaxiphora Gray, 1847
          • Placiphorina Kaas & Van Belle, 1994
          • Nuttallochiton Plate, 1899
          • Mopalia Gray, 1847
          • Placiphorella (Carpenter MS) Dall, 1879
          • Katharina Gray, 1847
          • Amicula Gray, 1847
        • Superfamily Cryptoplacoidea H. et A. Adams, 1858
        • Family Acanthochitonidae Pilsbry, 1893
        • Subfamily Acanthochitoninae Pilsbry, 1893
          • Acanthochitona Gray, 1921
          • Craspedochiton Shuttleworth, 1853
          • Spongiochiton (Carpenter MS) Dall, 1882
          • Notoplax H. Adams, 1861
          • Pseudotonicia Ashby, 1928
          • Bassethullia Pilsbry, 1928
          • Americhiton Watters, 1990
          • Choneplax (Carpenter MS) Dall, 1882
          • Cryptoconchus (De Blainville MS) Burrow, 1815
        • Subfamily Cryptochitoninae Pilsbry, 1893
          • Cryptochiton Middendorff, 1847
        • Family Hemiarthridae Sirenko, 1997
          • Hemiarthrum Carpenter in Dall, 1876
          • Weedingia Kaas, 1988
        • Family Choriplacidae Ashby, 1928
          • Choriplax Pilsbry, 1894
        • Family Cryptoplacidae H. et A. Adams, 1858
          • Cryptoplax de Blainville, 1818
  • Incertae sedis
    • • • Family Scanochitonidae Bergenhayn, 1955
          • Scanochiton Bergenhayn, 1955
        • Family Olingechitonidae Starobogatov et Sirenko, 1977
          • Olingechiton Bergenhayn, 1943
        • Family Haeggochitonidae Sirenko et Starobogatov, 1977
          • Haeggochiton Bergenhayn, 1955
        • Family Ivoechitonidae Sirenko et Starobogatov, 1977
          • Ivoechiton Bergenhayn, 1955

Habitat

Chitons are found in the littoral zone at the edge of the ocean throughout most of the world. Some species are found at depths of 6000 meters. A littoral is the region near the shoreline of a body of fresh or salt water. ...

Lined Chitons range from Northern Japan around the Aluetians to California. It is found in both the Intertidal and Subtidal zones, commonly on rocky surfaces. Chitons are particularly diverse and abundant in the shores of South Australia. Aleutians seen from space The Aleutian Islands (possibly from Chukchi aliat, island) are a chain of more than 300 small volcanic islands forming an island arc in the Northern Pacific Ocean, occupying an area of 6,821 sq mi (17,666 km²) and extending about 1,200 mi (1,900... Official language(s) English Capital Sacramento Largest city Los Angeles Area  Ranked 3rd  - Total 158,302 sq mi (410,000 km²)  - Width 250 miles (400 km)  - Length 770 miles (1,240 km)  - % water 4. ... A rock, seen at low tide, exhibiting typical intertidal zonation. ...

Miscellaneous

The largest chiton (up to 33 cm in length) is the brick-red gumboot chiton of the Pacific Northwest. Binomial name Cryptochiton stelleri (Middendorff, 1847) The Gumboot chiton (Cryptochiton stelleri), also known as the Giant Pacific chiton, is the largest member of the chiton family, growing to 33 centimeters (13 in). ... The Pacific Northwest from space This page is about the region that includes parts of Canada and the United States. ...

A possible Pre-Cambrian ancestor is Kimberella. It may also share a connection to Wiwaxia. Kimberella quadrata is a fossil animal from the Ediacaran or Vendian fauna. ... Binomial name Wiwaxia corrugata Walcott, 1911 Wiwaxia corrugata is an extinct species of animal known only from fossils found in Canadas Burgess Shale deposits. ...

References

1. ^ TSN 78807. Integrated Taxonomic Information System.
2. ^ American Heritage dictionary of the English Language: Fourth Edition. 2000. entry for chiton

Sirenko BI. New outlook on the system of chitons (Mollusca: Polyplacophora). Venus, 65 (1-2): 27-49, 2006 Please note that the ITIS system URL has changed (25 September 2006). ...

External links

• Extensive list of species, classified by families