Fish are aquatic vertebrates that are cold-blooded, covered with scales, and equipped with two sets of paired fins and several unpaired fins. Fish are abundant in the sea and in fresh water, with species being known from mountain streams (e.g., char and gudgeon) as well as in the deepest depths of the ocean (e.g., gulpers and anglerfish). They are of tremendous importance as food for people around the world, either collected from the wild (see fishing) or farmed in much the same way as cattle or chickens (see aquaculture). Fish are also exploited for recreation, through angling and fishkeeping, and fish are commonly exhibited in public aquaria. Fish have an important role in many cultures through the ages, ranging as widely as deities and religious symbols to subjects of books and popular movies. Look up fish in Wiktionary, the free dictionary. ... Various species of reef fish in the Hawaiian Islands. ... This article does not cite any references or sources. ... This article needs to be cleaned up to conform to a higher standard of quality. ... In this SEM image of a butterfly wing the scales are clearly visible, and the tiny platelets on each individual scale are just barely visible in the striping. ... A fin is a surface used to produce lift and thrust or to steer while traveling in water, air, or other fluid media. ... Species (see text) Salvelinus is a genus of Salmonid fish, referring to charizard or charr. ... Gudgeon is a common name for a number of small freshwater fishes of the families Cyprinidae, Eleotridae or Ptereleotridae. ... Families Cyematidae Saccopharyngidae Eupharyngidae Monognathidae Saccopharyngiformes is an order of unusual ray-finned fish superficially similar to eels, but with many internal differences. ... Suborders Antennarioidei Lophioidei Ogcocephalioidei See text for families. ... Fishing is the activity of hunting for fish by hooking, trapping, or gathering. ... Workers harvest catfish from the Delta Pride Catfish farms in Mississippi Aquaculture is the cultivation of aquatic organisms. ... Angling is a method of fishing, specifically the practice of catching fish by means of an angle (hook). ... This article or section does not cite any references or sources. ... “Aquaria” redirects here. ...

A giant grouper at the Georgia Aquarium, seen swimming among schools of other fish

Image File history File links Download high-resolution version (1200x1330, 407 KB) A giant grouper taken at the Georgia Aquarium on January 23rd by myself with a Canon 5D and 24-105mm f/4L IS. Taken by Diliff Edited by Fir0002. ... Image File history File links Download high-resolution version (1200x1330, 407 KB) A giant grouper taken at the Georgia Aquarium on January 23rd by myself with a Canon 5D and 24-105mm f/4L IS. Taken by Diliff Edited by Fir0002. ... Genera Acanthistius Alphestes Anyperidon Caprodon Cephalopholis Cromileptes Dermatolepis Epinephelus Gonioplectrus Gracila HypoplectrodesLiopropoma Mycteroperca Niphon Paranthias Plectropomus Saloptia Triso Variola For the computer program, see Grouper (Windows application). ... The Georgia Aquarium, located in Atlanta, Georgia at Pemberton Place, is billed as the worlds largest aquarium with more than 8 million US gallons (30,000 m³; 30,000,000 liters) of marine and fresh water, 1. ...

[edit] Definition

The term "fish" is most precisely used to describe any non-tetrapod chordate, i.e., an animal with a backbone that has gills throughout life and has limbs, if any, in the shape of fins.^[1] Unlike groupings such as birds or mammals, fish are not a single clade but a paraphyletic collection of taxa, including hagfishes, lampreys, sharks and rays, ray-finned fishes, coelacanths, and lungfishes.^[2][3] Groups See text. ... Typical Classes See below Chordates (phylum Chordata) are a group of animals that includes the vertebrates, together with several closely related invertebrates. ... For other uses, see Gill (disambiguation). ... For other uses, see Bird (disambiguation). ... Subclasses & Infraclasses Subclass †Allotheria* Subclass Prototheria Subclass Theria Infraclass †Trituberculata Infraclass Metatheria Infraclass Eutheria Mammals (class Mammalia) are warm-blooded, vertebrate animals characterized by the presence of sweat glands, including milk producing sweat glands, and by the presence of: hair, three middle ear bones used in hearing, and a neocortex... A clade is a term belonging to the discipline of cladistics. ... Paraphyletic - Wikipedia /**/ @import /skins-1. ... A taxon (plural taxa), or taxonomic unit, is a grouping of organisms (named or unnamed). ... Genera Eptatretus Myxine Nemamyxine Neomyxine Notomyxine Paramyxine Quadratus This article is about the Hagfish. ... Subfamilies Geotriinae Mordaciinae Petromyzontinae A lamprey (sometimes also called lamprey eel) is a jawless fish with a toothed, funnel-like sucking mouth. ... Subclasses and Orders See text. ... Orders See text The Actinopterygii are the ray-finned fish. ... Species Latimeria chalumnae Latimeria menadoensis Coelacanths (pronounced SEE-le-canth, meaning hollow spine in Greek) are lobe_finned fish with the pectoral and anal fins on fleshy stalks supported by bones, and the tail fin divided into three lobes, the middle one of which also has a stalk. ... For the musical band, see Lungfish (band). ...

A typical fish is cold-blooded; has a streamlined body that allows it to swim rapidly; extracts oxygen from the water using gills or an accessory breathing organ to enable it to breath atmospheric oxygen; has two sets of paired fins, usually one or two (rarely three) dorsal fins, an anal fin, and a tail fin; has jaws; has skin that is usually covered with scales; and lays eggs that are fertilized internally or externally. This article needs to be cleaned up to conform to a higher standard of quality. ... Solid blue lines and broken grey lines represent the streamlines. ... In this SEM image of a butterfly wing the scales are clearly visible, and the tiny platelets on each individual scale are just barely visible in the striping. ...

Fish come in many shapes and sizes. This is a sea dragon, a close relative of the seahorse. Their leaf-like appendages enable them to blend in with floating seaweed

To each of these there are exceptions. Tuna, Swordfish, and some species of sharks show some warm-blooded adaptations, and are able to raise their body temperature significantly above that of the ambient water surrounding them.^[4] Streamlining and swimming performance varies from highly streamlined and rapid swimmers which are able to reach 10-20 body-lengths per second (such as tuna, salmon, and jacks) through to slow but more maneuverable species such as eels and rays that reach no more than 0.5 body-lengths per second.^[5] Many groups of freshwater fish extract oxygen from the air as well as from the water using a variety of different structures. Lungfish have paired lungs similar to those of tetrapods, gouramis have a structure called the labyrinth organ that performs a similar function, while many catfish, such as Corydoras extract oxygen via the intestine or stomach.^[6] Body shape and the arrangement of the fins is highly variable, covering such seemingly un-fishlike forms as seahorses, pufferfish, anglerfish, and gulpers. Similarly, the surface of the skin may be naked (as in moray eels), or covered with scales of a variety of different types usually defined as placoid (typical of sharks and rays), cosmoid (fossil lungfishes and coelacanths), ganoid (various fossil fishes but also living gars and bichirs, cycloid, and ctenoid (these last two are found on most bony fish.^[7] There are even fishes that spend most of their time out of water. Mudskippers feed and interact with one another on mudflats and are only underwater when hiding in their burrows.^[8] The catfish Phreatobius cisternarum lives in underground, phreatic habitats, and a relative lives in waterlogged leaf litter.^[9][10] Image File history File linksMetadata Leafydragon. ... Image File history File linksMetadata Leafydragon. ... Binomial name (Günther, 1865) The leafy sea dragon, Phycodurus eques, is a marine fish related to the seahorse. ... This article is about the animal. ... For other uses, see Tuna (disambiguation). ... This article is about a type of fish. ... For other uses, see Shark (disambiguation). ... A warm-blooded (homeothermic) animal is one that can keep its core body temperature at a nearly constant level regardless of the temperature of the surrounding environment (that is, to maintain thermal homeostasis) . This can involve not only the ability to generate heat, but also the ability to cool down... A family of fishes which includes the Pompanos and Jacks Pilot fish - Naucrates ductor Categories: Fish stubs ... For other uses, see Eel (disambiguation). ... Orders Rajiformes - common rays and skates Pristiformes - sawfishes Torpediniformes - electric rays See text for families. ... Orders See text. ... Genera Belontiinae Belontia Luciocephalus/Trichogastrinae Colisa Ctenops Luciocephalus Parasphaerichthys Polyacanthus Sphaerichthys Trichogaster Macropodinae Betta Macropodus Malpulutta Parosphromenus Pseudosphromenus Trichopsis Osphroneminae Belontia Osphronemus The gouramies are a family Osphronemidae of freshwater perciform fish. ... A much folded suprabranchial accessory breathing organ found in Anabantoidei. ... Diversity Over 150 valid species. ... This article is about the animal. ... Genera Amblyrhynchotes Arothron Auriglobus Canthigaster Carinotetraodon Chelonodon Colomesus Contusus Ephippion Feroxodon Fugu Gastrophysus Javichthys Lagocephalus Liosaccus Marilyna Monotretus Omegaphora Pelagocephalus Polyspina Reicheltia Sphoeroides Takifugu Tetractenos Tetraodon Torquigener Tylerius Xenopterus For species see Genera articles. ... Suborders Antennarioidei Lophioidei Ogcocephalioidei See text for families. ... Families Cyematidae Eurypharyngidae Monognathidae Saccopharyngidae Saccopharyngiformes is an order of unusual ray-finned fish superficially similar to eels, but with many internal differences. ... Genera See text. ... Denticles or placoid scales are small outgrowths which cover the skin of many cartilaginous fish including sharks. ... In this SEM image of a butterfly wing the scales are clearly visible, and the tiny platelets on each individual scale are just barely visible in the striping. ... In most biological nomenclature, a scale (Greek lepid, Latin squama) is a small rigid plate that grows out of an animals skin to provide protection. ... Species Atractosteus spatula Atractosteus tristoechus Atractosteus tropicus Lepisosteus oculatus Lepisosteus osseus Lepisosteus platostomus Lepisosteus platyrhincus In American English the name gar (or garpike) is strictly applied to members of the Lepisosteidae, a family including seven living species of fish in two genera that inhabit fresh, brackish, and occasionally marine, waters... Genera Erpetoichthys Polypterus See text for species. ... Cycloid (red) generated by a rolling circle A cycloid is the curve defined by a fixed point on a wheel as it rolls, or, more precisely, the locus of a point on the rim of a circle rolling along a straight line. ... This page is a candidate to be copied to Wiktionary. ... Subclasses Actinopterygii Sarcopterygii Osteichthyes are the bony fish, a group paraphyletic to the land vertebrates, which are sometimes included. ... Genera Apocryptes Apocryptodon Boleophthalmus Oxuderces Parapocryptes Periophthalmodon Periophthalmus Pseudapocryptes Scartelaos Zappa (genus) Mudskippers are members of the subfamily Oxudercinae (tribe: Periophthalmini[1]), within the family Gobiidae (Gobies). ... This article is about the siluriform catfishes; for the Atlantic catfish, see Seawolf (fish); for other uses, see Catfish (disambiguation). ... Binomial name Phreatobius cisternarum Goeldi, 1905 Phreatobius cisternarum is the only species of catfish in the genus Phreatobius. ... The term phreatic is used in geology to refer to matters relating to underground water below the water table (the word originates from the Greek phrear, phreat- meaning well or spring). The phreatic zone is the layer(s) of soil or rock below the water table in which voids are... Fungus growing in leaf litter Leaf litter (sometimes called leaf mold or tree litter) is the layer of leaves and other forms of decomposing matter found on the ground beneath vegetation. ...

Fish range in size from the 16 m (51 ft) whale shark to the 8 mm (just over ¼ of an inch) long stout infantfish. Binomial name (Smith, 1828) Range of whale shark The whale shark, Rhincodon typus, is a slow filter feeding shark that is the largest living fish species. ... Binomial name Schindleria brevipinguis Watson & Walker, 2004 Schindleria brevipinguis is a species of marine fish in family Schindleriidae of Perciformes. ...

Many types of aquatic animals commonly referred to as "fish" are not fish in the sense given above; examples include shellfish, crayfish and jellyfish. In some contexts, especially in aquaculture, the true fish are referred to finfish to distinguish them from these other animals. Animal environments are classified as either aquatic (water), terrestrial (land), or amphibious (water and land). ... Cooked mussels Shellfish is a term used to describe shelled molluscs and crustaceans used as food. ... Families Astacoidea   Astacidae   Cambaridae Parastacoidea   Parastacidae Crayfish, often referred to as crawfish or crawdad, are freshwater crustaceans resembling small lobsters, to which they are closely related. ... Bold text For other uses, see Jellyfish (disambiguation). ...

[edit] Classification

Fish are a paraphyletic group: that is, any clade containing all fish also contains the tetrapods, which are not fish. For this reason, groups such as the "Class Pisces" seen in older reference works are no longer used in formal classifications. In phylogenetics, a grouping of organisms is said to be paraphyletic (Greek para = near and phyle = race) if all the members of the group have a common ancestor, but the group does not include all the descendants of the most recent common ancestor of all group members. ... A clade is a term belonging to the discipline of cladistics. ... Groups See text. ...

Some palaeontologists consider that Conodonta are chordates, and so regard them as primitive fish. For a fuller treatment of classification, see the vertebrate article. Orders Arandaspida Heterostraci Thelodontidae Eriptychiida Astraspida Pteraspidomorphi is an extinct subclass of early jawless fish. ... Subgroupings (unranked, see Turner 1991) Theleodontina Loganiida Katoporida There is much debate over whether the clade of Palaeozoic fish known as the Thelodonti represent a monophyletic grouping, or disparate stem groups to the major lines of jawless and jawed fish. ... Anaspida are a extinct marine subgroup of the agnatha. ... subgroups Osteostraci Galeaspida Pituriaspida Anaspida Hyperoartia (lampreys) Cephalaspidomorphs are a taxon of jawless fishes named for the cephalaspids, which is another name for the osteostracans. ... Subfamilies Geotriinae Mordaciinae Petromyzontinae A lamprey is a jawless fish with a toothed, funnel-like sucking mouth, with which most species bore into the flesh of other fishes to suck their blood. ... Subfamilies Geotriinae Mordaciinae Petromyzontinae A lamprey is a type of fish with a toothed, funnel-like, jawless sucking mouth, with which most species bore into the flesh of other fishes to suck their blood. ... Subfamilies Geotriinae Mordaciinae Petromyzontinae A lamprey (sometimes also called lamprey eel) is a jawless fish with a toothed, funnel-like sucking mouth. ... Galeaspida (galeaspids) are an extinct taxon of jawless marine fish and a subgroup of the Cephalaspidomorphi, which are itself a subgroup of the vertebrate. ... Pituriaspida are an extinct taxon of jawless marine fish and a subgroup of the Cephalaspidomorphi, which are itself a subgroup of the vertebrate. ... Osteostraci (Cephalaspidiformes) are an extinct marine subgroup of the agnatha. ... Classes Placodermi Chondrichthyes Acanthodii Osteichthyes Gnathostomata is the group of vertebrates with jaws. ... Orders Antiarchi † Arthrodira † Brindabellaspida † Petalichthyida † Phyllolepida † Ptyctodontida † Rhenanida † Acanthothoraci † ?Pseudopetalichthyida † ?Stensioellida † The Placodermi are armoured prehistoric fishes known from fossils dating from the late Silurian to the end of the Devonian Period. ... Subclasses and Orders See text. ... Orders Climatiiformes Ischnacanthiformes Acanthodiformes Acanthodii (sometimes called spiny sharks) is a class of extinct fishes, having features of both bony fish (Osteichthyes) and cartilaginous fish (Chondrichthyes). ... Classes Actinopterygii Sarcopterygii Osteichthyes are a taxonomic superclass of fish, also called bony fish that includes the ray-finned fish (Actinopterygii) and lobe finned fish (Sarcopterygii). ... Orders See text The Actinopterygii are the ray-finned fish. ... Subclasses Coelacanthimorpha - Coelacanths Dipnoi - Lungfishes Tetrapoda Sarcopterygii is traditionally the class of lobe-finned fishes, consisting of lungfish and coelacanths. ... Species Latimeria chalumnae Latimeria menadoensis Coelacanths (pronounced SEE-le-canth, meaning hollow spine in Greek) are lobe_finned fish with the pectoral and anal fins on fleshy stalks supported by bones, and the tail fin divided into three lobes, the middle one of which also has a stalk. ... Families See text. ... For the musical band, see Lungfish (band). ... Orders See text. ... Conodont Conodonts are extinct worm-like forms with distinctive conical or multi-denticulate teeth made of apatite (calcium phosphate). ... Typical Classes See below Chordates (phylum Chordata) are a group of animals that includes the vertebrates, together with several closely related invertebrates. ... This article does not cite any references or sources. ...

The various fish groups taken together account for more than half of the known vertebrates. There are almost 28,000 known extant species of fish, of which almost 27,000 are bony fish, with the remainder being about 970 sharks, rays, and chimeras and about 108 hagfishes and lampreys.^[11] A third of all of these species are contained within the nine largest families; from largest to smallest, these families are Cyprinidae, Gobiidae, Cichlidae, Characidae, Loricariidae, Balitoridae, Serranidae, Labridae, and Scorpaenidae. On the other hand, about 64 families are monotypic, containing only one species. It is predicted that the eventual number of total extant species will be at least 32,500.^[12] In biology, extant taxon is commonly used in discussions of living and fossil species. ... Subclasses and Orders See text. ... Genera (many, see text) The family Cyprinidae, named after the Greek word for goldfish, consists of the carps and minnows. ... Genera Many, e. ... Genera Apistogramma - Dwarf Cichlids Astronotus (Oscars) Boulengerochromis Cichlasoma - American Ciclids Crenicichla Pterophyllum - Freshwater Angelfish Symphysodon - Discus Teleogramma Tilapia Cichlids are a family of perciform fishes. ... Subfamilies and Genera[2] Subfamily Agoniatinae  Agoniates Subfamily Aphyocharacinae  Aphyocharax Subfamily Bryconinae  Brycon  Chilobrycon  Henochilus Subfamily Characinae  Acanthocharax  Acestrocephalus  Charax  Cynopotamus  Galeocharax  Gnathocharax  Heterocharax  Hoplocharax  Phenacogaster  Priocharax  Roeboides  and many more Subfamily Cheirodontinae  Cheirodon  Compsura  Odontostilbe  Serrapinnus  Spintherobolus  and many more Subfamily Clupeacharacinae  Clupeacharax Subfamily Glandulocaudinae  20 genera Subfamily Iguanodectinae... Genera about 70, see text The armored catfishes are a family Loricariidae of catfish noted for the covering of bony plates covering their bodies. ... The hillstream loaches are a family (Balitoridae) of small Eurasian fish that generally live in fast-flowing streams and have a large sucker mouth and modified ventral fins used for clinging to rocks. ... Subfamilies Anthiinae Epinephelinae - Groupers Grammistinae The Serranidae or serranids are a family of fish, belonging to the order Perciformes. ... Genera (60 genera) The wrasses are a family (family Labridae) of reef safe marine fish, many of which are brightly-colored and popular for aquaria. ... Genera (many) The scorpionfishes or rockfishes are a family (Scorpaenidae) of mostly marine fish that includes many of the worlds most venomous species. ... Monotypic is an adjective, that refers to a taxonomic group with only one type: in botany it means that a taxon has only one species; Ginkgo is a monotypic genus, while Ginkgoaceae is a monotypic family. ...

[edit] Anatomy

Main article: Fish anatomy

The anatomy of Lampanyctodes hectoris
(1) - operculum (gill cover), (2) - lateral line, (3) - dorsal fin, (4) - fat fin, (5) - caudal peduncle, (6) - caudal fin, (7) - anal fin, (8) - photophores, (9) - pelvic fins (paired), (10) - pectoral fins (paired)

Fish anatomy is primarily governed by the physical characteristics of water, which is much denser than air, holds a relatively small amount of dissolved oxygen, and absorbs light more than air does. ... Image File history File links Download high-resolution version (2154x898, 465 KB) based on :Image:Lampanyctodes hectoris (Hectors lanternfish). ... Image File history File links Download high-resolution version (2154x898, 465 KB) based on :Image:Lampanyctodes hectoris (Hectors lanternfish). ...

[edit] Digestive system

The advent of jaws allowed fish to eat a much wider variety of food, including plants and other organisms. In fish, food is ingested through the mouth and then broken down in the esophagus. When it enters the stomach, the food is further broken down and, in many fish, further processed in fingerlike pouches called pyloric caeca. The pyloric caeca secrete digestive enzymes and absorb nutrients from the digested food. Organs such as the liver and pancreas add enzymes and various digestive chemicals as the food moves through the digestive tract. The intestine completes the process of digestion and nutrient absorption. The esophagus (also spelled oesophagus/Å“sophagus, Greek ), or gullet is an organ in vertebrates which consists of a muscular tube through which food passes from the pharynx to the stomach. ... Neuraminidase ribbon diagram An enzyme (in Greek en = in and zyme = blend) is a protein, or protein complex, that catalyzes a chemical reaction and also controls the 3D orientation of the catalyzed substrates. ... For the bird, see Liver bird. ... The pancreas is a gland organ in the digestive and endocrine systems of vertebrates. ...

[edit] Respiratory system

Most fish exchange gases by using gills that are located on either side of the pharynx. Gills are made up of threadlike structures called filaments. Each filament contains a network of capillaries that allow a large surface area for the exchange of oxygen and carbon dioxide. Fish exchange gases by pulling oxygen-rich water through their mouths and pumping it over their gill filaments. The blood in the capillaries flows in the opposite direction to the water, causing counter current exchange. They then push the oxygen-poor water out through openings in the sides of the pharynx. Some fishes, like sharks and lampreys, possess multiple gill openings. However, most fishes have a single gill opening on each side of the body. This opening is hidden beneath a protective bony cover called an operculum. For other uses, see Gill (disambiguation). ... The pharynx (plural: pharynges) is the part of the neck and throat situated immediately posterior to the mouth and nasal cavity, and cranial, or superior, to the esophagus, larynx, and trachea. ... Filaments surrounding a solar flare, caused by the interaction of the plasma in the Suns atmopshere with its magnetic field. ... Blood flows from digestive system heart to arteries, which narrow into arterioles, and then narrow further still into capillaries. ... Area is the measure of how much exposed area any two dimensional object has. ... General Name, symbol, number oxygen, O, 8 Chemical series nonmetals, chalcogens Group, period, block 16, 2, p Appearance colourless (gas) colourless (liquid) Standard atomic weight 15. ... Carbon dioxide is a chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom. ... It has been suggested that Counter-current heat exchange, Counter-current heat exchangers be merged into this article or section. ... For other uses, see Shark (disambiguation). ... Subfamilies Geotriinae Mordaciinae Petromyzontinae A lamprey (sometimes also called lamprey eel) is a jawless fish with a toothed, funnel-like sucking mouth. ... The operculum in fish is the hard bony flap covering and protecting the gills of Bony fish. ...

Juvenile bichirs have external gills, a very primitive feature that they hold in common with larval amphibians. Genera Erpetoichthys Polypterus See text for species. ... For other uses, see Amphibian (disambiguation). ...

Swim bladder of a Rudd (Scardinius erythrophthalmus)

Many fish can breathe air. The mechanisms for doing so are varied. The skin of anguillid eels may be used to absorb oxygen. The buccal cavity of the electric eel may be used to breathe air. Catfishes of the families Loricariidae, Callichthyidae, and Scoloplacidae are able to absorb air through their digestive tracts.^[13] Lungfish and bichirs have paired lungs similar to those of tetrapods and must rise to the surface of the water to gulp fresh air in through the mouth and pass spent air out through the gills. Gar and bowfin have a vascularised swim bladder that is used in the same way. Loaches, trahiras, and many catfish breathe by passing air through the gut. Mudskippers breathe by absorbing oxygen across the skin (similar to what frogs do). A number of fishes have evolved so-called accessory breathing organs that are used to extract oxygen from the air. Labyrinth fish (such as gouramis and bettas) have a labyrinth organ above the gills that performs this function. A few other fish have structures more or less resembling labyrinth organs in form and function, most notably snakeheads, pikeheads, and the Clariidae family of catfish. Image File history File linksMetadata Swim_bladder. ... Image File history File linksMetadata Swim_bladder. ... This article is about the animal. ... Genera about 70, see text The armored catfishes are a family Loricariidae of catfish noted for the covering of bony plates covering their bodies. ... Genera Aspidoras Brochis Callichthys Corydoras Dianema Hoplosternum Lepthoplosternum Megalechis Scleromystax The family Callichthyidae hails from South America and contains some of the most popular freshwater aquarium fish such as the corydoras. ... Species[1] Scoloplax is the only genus in the family (biology) Scoloplacidae, the spiny dwarf catfishes. ... Orders See text. ... Genera Erpetoichthys Polypterus See text for species. ... Groups See text. ... Species Atractosteus spatula Atractosteus tristoechus Atractosteus tropicus Lepisosteus oculatus Lepisosteus osseus Lepisosteus platostomus Lepisosteus platyrhincus In American English the name gar (or garpike) is strictly applied to members of the Lepisosteidae, a family including seven living species of fish in two genera that inhabit fresh, brackish, and occasionally marine, waters... Binomial name Amia calva Linnaeus, 1766 The bowfins are an order (Amiiformes) of primitive ray-finned fish. ... Genera Acanthopsoides Acanthophthalmus Acantopsis Botia Cobitis Crossostoma Enobarbichthys Formosiana Iksookimia Koreocobitis Lepidocephalichthys Lepidocephalus Leptobotia Misgurnus Neoeucirrhichthys Niwaella Pangio Parabotia Paralepidocephalus Paramisgurnus Protocobitis Sabanejewia Serpenticobitis Somileptes (Gongota loach) Loaches are freshwater fishes of the family Cobitidae, small benthic (bottom-dwelling) fishes with a flattened ventral profile. ... Genera Erythrinus Hoplerythrinus Hoplias The Erythrinidae, also known as Trahiras, are a family of freshwater fishes found in the rivers of South America. ... This article is about the siluriform catfishes; for the Atlantic catfish, see Seawolf (fish); for other uses, see Catfish (disambiguation). ... Genera Belontiinae Belontia Luciocephalus/Trichogastrinae Colisa Ctenops Luciocephalus Parasphaerichthys Polyacanthus Sphaerichthys Trichogaster Macropodinae Betta Macropodus Malpulutta Parosphromenus Pseudosphromenus Trichopsis Osphroneminae Belontia Osphronemus The gouramies are a family Osphronemidae of freshwater perciform fish. ... Betta Betta splendens which is often called simply betta, see Siamese fighting fish. ... The labyrinth organ is a much-folded suprabranchial accessory breathing organ found in labyrinth fish, of the Anabantoidei family. ... Genera Channa Parachanna Channidae is a family of freshwater perciform fish commonly known as snakeheads, and is native to Africa and Asia. ... Genera Allabenchelys Channallabes Clariallabes Clarias Dinotopteroides Dinotopterus Dolichallabes Encheloclarias Gymnallabes Heterobranchus Horaglanis Platyallabes Platyclarias Tanganikallabes Uegitglanis Xenoclarias Xenoglanis Airbreathing catfishes are fishes comprising the family Clariidae. ...

Being able to breathe air is primarily of use to fish that inhabit shallow, seasonally variable waters where the oxygen concentration in the water may decline at certain times of the year. At such times, fishes dependent solely on the oxygen in the water, such as perch and cichlids, will quickly suffocate, but air-breathing fish can survive for much longer, in some cases in water that is little more than wet mud. At the most extreme, some of these air-breathing fish are able to survive in damp burrows for weeks after the water has otherwise completely dried up, entering a state of aestivation until the water returns. Estivation or aestivation (from Latin aestas, summer) is a state of dormancy similar to hibernation. ...

Tuna gills inside of the head. The fish head is oriented snout-downwards, with the view looking towards the mouth.

Fish can be divided into obligate air breathers and facultative air breathers. Obligate air breathers, such as the African lungfish, must breathe air periodically or they will suffocate. Facultative air breathers, such as the catfish Hypostomus plecostomus, will only breathe air if they need to and will otherwise rely solely on their gills for oxygen if conditions are favourable. Most fish are not obligate air breathers as there is an energetic cost in rising to the surface and a fitness cost of being exposed to predators.^[13] Image File history File links Download high resolution version (1103x954, 303 KB) Tuna gills inside of the head. ... Image File history File links Download high resolution version (1103x954, 303 KB) Tuna gills inside of the head. ...

[edit] Circulatory system

Fish have a closed circulatory system with a heart that pumps the blood in a single loop throughout the body. The blood goes from the heart to gills, from the gills to the rest of the body, and then back to the heart. In most fish, the heart consists of four parts: the sinus venosus, the atrium, the ventricle, and the bulbus arteriosus. Despite consisting of four parts, the fish heart is still a two-chambered heart.^[14] The sinus venosus is a thin-walled sac that collects blood from the fish's veins before allowing it to flow to the atrium, which is a large muscular chamber. The atrium serves as a one-way compartment for blood to flow into the ventricle. The ventricle is a thick-walled, muscular chamber and it does the actual pumping for the heart. It pumps blood to a large tube called the bulbus arteriosus. At the front end, the bulbus arteriosus connects to a large blood vessel called the aorta, through which blood flows to the fish's gills. For transport in plants, see Vascular tissue. ... The heart and lungs, from an older edition of Grays Anatomy. ... Human blood smear: a - erythrocytes; b - neutrophil; c - eosinophil; d - lymphocyte. ... Sinus venosus can refer to: Another name for the embryological structure Sinus venarum A type of atrial septal defect This is a disambiguation page: a list of articles associated with the same title. ... In anatomy, the atrium (plural: atria) refers to a chamber or space. ... In the heart, a ventricle is a heart chamber which collects blood from an atrium (another heart chamber that is smaller than a ventricle) and pumps it out of the heart. ... In the circulatory system, a vein is a blood vessel that carries blood toward the heart. ...

[edit] Excretory system

As with many aquatic animals, most fish release their nitrogenous wastes as ammonia. Some of the wastes diffuse through the gills into the surrounding water. Others are removed by the kidneys, excretory organs that filter wastes from the blood. Kidneys help fishes control the amount of ammonia in their bodies. Saltwater fish tend to lose water because of osmosis. In saltwater fish, the kidneys concentrate wastes and return as much water as possible back to the body. The reverse happens in freshwater fish, they tend to gain water continuously. The kidneys of freshwater fish are specially adapted to pump out large amounts of dilute urine. Some fish have specially adapted kidneys that change their function, allowing them to move from freshwater to saltwater. For other uses, see Ammonia (disambiguation). ... diffusion (disambiguation). ... The kidneys are the organs that filter wastes (such as urea) from the blood and excrete them, along with water, as urine. ... In chemistry and common usage, a filter is a device (usually a membrane or layer) that is designed to block certain objects or substances while letting others through. ... Osmosis is the spontaneous net movement of water across a semipermeable membrane from a region of low solute concentration to a solution with a high solute concentration, down a solute concentration gradient. ... A vast number of species of fish have been successfully kept in the home aquarium. ...

[edit] Sensory and nervous system

Dorsal view of the brain of the rainbow trout.

Image File history File links Size of this preview: 343 × 600 pixelsFull resolution (690 × 1206 pixels, file size: 98 KB, MIME type: image/png) Schematic dorsal view of the brain of a trout (Oncorhynchus mykiss) with key features labelled. ... Image File history File links Size of this preview: 343 × 600 pixelsFull resolution (690 × 1206 pixels, file size: 98 KB, MIME type: image/png) Schematic dorsal view of the brain of a trout (Oncorhynchus mykiss) with key features labelled. ... It has been suggested that Steelhead be merged into this article or section. ...

[edit] Central nervous system

Fish typically have quite small brains relative to body size when compared with other vertebrates, typically one-fifteenth the mass of the brain from a similarly sized bird or mammal.^[15] However, some fishes have relatively large brains, most notably mormyrids and sharks, which have brains of about as massive relative to body weight as birds and marsupials.^[16] Human brain In animals, the brain (enkephale) (Greek for in the skull), is the control center of the central nervous system, responsible for behavior. ... Subfamilies Mormyrinae Petrocephalinae The family Mormyridae, sometimes called Elephantfish, are freshwater fishes native to Africa in the order Osteoglossiformes. ... For other uses, see Shark (disambiguation). ... For other uses, see Bird (disambiguation). ... This article is about mammals. ...

The brain is divided into several regions. At the front are the olfactory lobes, a pair of structure the receive and process signals from the nostrils via the two olfactory nerves.^[15] The olfactory lobes are very large in fishes that hunt primarily by smell, such as hagfish, sharks, and catfish. Behind the olfactory lobes is the two-lobed telencephalon, the equivalent structure to the cerebrum in higher vertebrates. In fishes the telencephalon is concerned mostly with olfaction.^[15] Together these structures form the forebrain. The olfactory bulb is a structure of the vertebrate forebrain involved in olfaction, the perception of odors. ... A nostril is one of the two channels of the nose, from the point where they bifurcate to the external opening. ... The olfactory nerve is the first of twelve cranial nerves. ... The telencephalon (te-len-seff-a-lon) is the technical name for a large region within the brain which is attributed many functions, which some groups would class as unique features which make humans stand out from other species. ... The telencephalon (IPA: ) is the name for the forebrain, a large region within the brain to which many functions are attributed. ... Olfaction (also known as olfactics) refers to the sense of smell. ...

Connecting the forebrain to the midbrain is the diencephalon (in the adjacent diagram, this structure is below the optic lobes and consequently not visible). The diencephalon performs a number of functions associated with hormones and homeostasis.^[15] The pineal body lies just above the diencephalon. This structure performs many different functions including detecting light, maintaining circadian rhythms, and controlling colour changes.^[15] The diencephalon is the region of the brain that includes the epithalamus, thalamus, and hypothalamus. ... For other uses, see Hormone (disambiguation). ... Homeostasis is the property of either an open system or a closed system, especially a living organism, which regulates its internal environment so as to maintain a stable, constant condition. ... The pineal gland (pronunciation: pI-nE-&l, pI-), or epiphysis, is a small endocrine gland located near the middle of the brain. ... The circadian rhythm is a name given to the internal body clock that regulates the (roughly) 24 hour cycle of biological processes in animals and plants. ...

The midbrain or mesencephalon contains the two optic lobes. These are very large in species that hunt by sight, such as rainbow trout and cichlids.^[15] In biological anatomy, the mesencephalon (or midbrain) is the middle of three vesicles that arise from the neural tube that forms the brain of developing animals. ... Optic Lobe: It is inside the brain, and it indicates to either of two lobes of the dorsal mesencephalon, containing primary visual centers. ... It has been suggested that Steelhead be merged into this article or section. ... Subfamilies Astronotinae Cichlasomatinae Cichlinae Etroplinae Geophaginae Heterochromidinae Paratilapiinae Pseudocrenilabrinae Ptychochrominae Retroculinae For genera, see below. ...

The hindbrain or metencephalon is particularly involved in swimming and balance.^[15] The cerebellum is a single-lobed structure that is usually very large, typically the biggest part of the brain.^[15] Hagfish and lampreys have relatively small cerebellums, but at the other extreme the cerebellums of mormyrids are massively developed and apparently involved in their electrical sense.^[15] The metencephalon is a developmental categorization of portions of the central nervous system. ... Subfamilies Geotriinae Mordaciinae Petromyzontinae A lamprey (sometimes also called lamprey eel) is a jawless fish with a toothed, funnel-like sucking mouth. ... Subfamilies Mormyrinae Petrocephalinae The familly Mormyridae, sometimes called Elephantfish, are freshwater fishes native to Africa. ... An electric fish is a fish that can generate electric field]s. ...

The brain stem or myelencephalon is the most posterior part of the brain.^[15] As well as controlling the functions of some of the muscles and body organs, in bony fish at least the brain stem is also concerned with respiration and osmoregulation.^[15] The myelencephalon is a developmental categorization of a portion of the central nervous system. ... Look up Respiration in Wiktionary, the free dictionary. ... Osmoregulation is the active regulation of the osmotic pressure of bodily fluids to maintain the homeostasis of the bodys water content; that is it keeps the bodys fluids from becoming too dilute or too concentrated. ...

[edit] Sense organs

Most fish possess highly developed sense organs. Nearly all daylight fish have well-developed eyes that have color vision that is at least as good as a human's. Many fish also have specialized cells known as chemoreceptors that are responsible for extraordinary senses of taste and smell. Although they have ears in their heads, many fish may not hear sounds very well. However, most fishes have sensitive receptors that form the lateral line system. The lateral line system allows for many fish to detect gentle currents and vibrations, as well as to sense the motion of other nearby fish and prey.^[17] Some fishes such as catfishes and sharks, have organs that detect low levels electric current.^[18] Other fish, like the electric eel, can produce their own electricity. In fish, the lateral line is a sense organ used to detect movement and vibration in the surrounding water. ...

[edit] Pain reception in fish

In 2003, it was concluded by Scottish scientists at the University of Edinburgh performing research on rainbow trout that fish exhibit behaviors often associated with pain.^[19] Professor James D. Rose of the University of Wyoming found flaws in the study and published a critique of it.^[20] Rose had published his own study a year earlier concluding that fish cannot feel pain as they lack the appropriate neocortex of the brain.^[21] Other researchers have suggested that the question of pain in fish may be diffcult to answer since fish "pain" might be felt differently than human "pain."^[22] This article is about the profession. ... The University of Edinburgh (Scottish Gaelic: ), founded in 1582,[4] is a renowned centre for teaching and research in Edinburgh, Scotland. ... Look up Pain in Wiktionary, the free dictionary. ... The University of Wyoming is a land-grant university located in Laramie, Wyoming, situated on Wyomings high Laramie Plains, at an elevation of 7,200 feet (2194 m), between the the Laramie and Snowy Range mountains. ... The neocortex (Latin for new bark or new rind) is a part of the brain of mammals. ...

[edit] Muscular system

Main article: Fish locomotion

Most fish move by contracting paired sets of muscles on either side of the backbone alternately. These contractions form S-shaped curves that move down the body of the fish. As each curve reaches the back fin, backward force is created. This backward force, in conjunction with the fins, moves the fish forward. The fish's fins are used like an airplane's stabilizers. Fins also increase the surface area of the tail, allowing for an extra boost in speed. The streamlined body of the fish decreases the amount of friction as they move through water. Since body tissue is more dense than water, fish must compensate for the difference or they will sink. Many bony fishes have an internal organ called a swim bladder that adjust their buoyancy through manipulation of gases. Fish swim by exerting force against the surrounding water. ... The gas bladder (also fish maw, less accurately swim bladder or air bladder) is an internal organ that contributes to the ability of a fish to control its buoyancy, and thus to stay at the current water depth, ascend, or descend without having to waste energy in swimming. ...

[edit] Reproductive system

Further information: Spawning

Frog spawn Spawning is the production or depositing of eggs in large numbers by aquatic animals. ...

[edit] Organs

Fish reproductive organs include testes and ovaries. In most fish species, gonads are paired organs of similar size, which can be partially or totally fused.^[23] There may also be a range of secondary reproductive organs that help in increasing a fish's fitness. Look up testes in Wiktionary, the free dictionary. ... // For ovary as part of plants see ovary (plants) An ovary is an egg-producing reproductive organ found in female organisms. ...

In terms of spermatogonia distribution, the structure of teleosts testes has two types: in the most common, spermatogonia occur all along the seminiferous tubules, while in Atherinomorph fishes they are confined to the distal portion of these structures. Fishes can present cystic or semi-cystic spermatogenesis in relation to the phase of release of germ cells in cysts to the seminiferous tubules lumen.^[23] The introduction of this article does not provide enough context for readers unfamiliar with the subject. ... Cross section of the epithelium of a seminiferous tubule showing various stages of spermatocyte development Spermatogenesis is the process by which male spermatogonia develop into mature spermatozoa. ...

Fish ovaries may be of two types: gymnovarian or cystovarian. In the first type, the oocytes are released directly into the coelomic cavity and then eliminated. In the second type, the oocytes are conveyed to the exterior through the oviduct.^[24] Gymnovaries are the primitive condition found in lungfishes, sturgeons, and bowfins. Cystovaries are the condition that characterizes most of the teleosts, where the ovary lumen has continuity with the oviduct.^[23] A body cavity is an aspect of a number of basic animal body plans (phyla) that incorporate a central body cavity, known as a coelom. ... In oviparous animals (those that lay eggs), the passage from the ovaries to the outside of the body is known as the oviduct. ...

Oogonia development in teleosts fish varies according to the group, and the determination of oogenesis dynamics allows the understanding of maturation and fertilization processes. Changes in the nucleus, ooplasm, and the surrounding layers characterize the oocyte maturation process.^[23]

Postovulatory follicles are structures formed after oocyte release; they do not have endocrine function, present a wide irregular lumen, and are rapidly reabosrbed in a process involving the apoptosis of follicular cells. A degenerative process called follicular atresia reabsorbs vitellogenic oocytes not spawned. This process can also occur, but less frequently, in oocytes in other development stages.^[23] The endocrine system is a control system of ductless endocrine glands that secrete chemical messengers called hormones that circulate within the body via the bloodstream to affect distant organs. ...

Some fish are hermaphrodites, either having testes and ovaries at different phases in the life cycle. However, there are even some fish, such as hamlets, that are simultaneously male and female. For other uses, see Hermaphrodite (disambiguation). ... - A hamlet is a fish of the genus Hypoplectrus. ...

[edit] Reproductive method

Over 97% of all known fishes are oviparous,^[25] that is, the eggs develop outside the mother's body. Examples of oviparous fishes include salmon, goldfish, cichlids, tuna, and eels. In the majority of these species, fertilisation takes place outside the mother's body, with the male and female fish shedding their gametes into the surrounding water. However, a few oviparous fishes practise internal fertilisation, with the male using some sort of intromittent organ to deliver sperm into the genital opening of the female, most notably the oviparous sharks, such as the horn shark, and oviparous rays, such as skates. In these cases, the male is equipped with a pair of modified pelvic fins known as claspers. For other uses, see Salmon (disambiguation). ... Trinomial name Carassius auratus auratus (Linnaeus, 1758) For the baked snack crackers, please see Goldfish (snack). ... Subfamilies Astronotinae Cichlasomatinae Cichlinae Etroplinae Geophaginae Heterochromidinae Paratilapiinae Pseudocrenilabrinae Ptychochrominae Retroculinae For genera, see below. ... For other uses, see Tuna (disambiguation). ... For other uses, see Eel (disambiguation). ... A gamete (from Ancient Greek γαμετης; translated gamete = wife, gametes = husband) is a cell that fuses with another gamete during fertilization (conception) in organisms that reproduce sexually. ... Ichthyology uses several terms that are unique to the science. ... Binomial name Heterodontus francisci Girard, 1855 The Horn shark (Heterodontus francisci) is a shark from the bullhead shark order Heterodontiformes. ... Broad skate, Amblyraja badia A skate egg case, known as a mermaids purse. ... Human male pelvis, viewed from front Human female pelvis, viewed from front The pelvis is the bony structure located at the base of the spine (properly known as the caudal end). ... The claspers of a wobbegong shark (Orectolobus maculatus). ...

The newly-hatched young of oviparous fish are called larvae. They are usually poorly formed, carry a large yolk sac (from which they gain their nutrition) and are very different in appearance to juvenile and adult specimens of their species. The larval period in oviparous fish is relatively short however (usually only several weeks), and larvae rapidly grow and change appearance and structure (a process termed metamorphosis) to resemble juveniles of their species. During this transition larvae use up their yolk sac and must switch from yolk sac nutrition to feeding on zooplankton prey, a process which is dependent on zooplankton prey densities and causes many mortalities in larvae. A larval insect A larva (Latin; plural larvae) is a juvenile form of animal with indirect development, undergoing metamorphosis (for example, insects or amphibians). ... The yolk sac is the first element seen in the gestational sac during pregnancy, usually at 5 weeks gestation. ... A cicada in the process of shedding. ... Photomontage of plankton organisms Plankton is the aggregate community of weakly swimming but mostly drifting small organisms that inhabit the water column of the ocean, seas, and bodies of freshwater. ...

Ovoviviparous fish are ones in which the eggs develop inside the mother's body after internal fertilization but receive little or no nutrition from the mother, depending instead on the yolk. Each embryo develops in its own egg. Familiar examples of ovoviviparous fishes include guppies, angel sharks, and coelacanths. Ovoviviparous animals develop within eggs that remain within the mother up until they hatch