Fish anatomy is the study of the form or morphology of fishes. It can be contrasted with fish physiology, the study of how the component parts of fish function together in the living fish. In practice, fish anatomy and fish physiology complement each other, the former dealing with the structure of a fish, its organs or component parts and how they are put together, such as might be observed on the dissecting table or under the microscope, the latter dealing with how those components function together in living fish; the anatomy of fish is shaped by the physical characteristics of water, the medium in which fish live. Water is much denser than air, holds a small amount of dissolved oxygen, absorbs more light than air does; the body of a fish is divided into a head and tail, although the divisions between the three are not always externally visible. The skeleton, which forms the support structure inside the fish, is either made of cartilage, in cartilaginous fish, or bone in bony fish; the main skeletal element is the vertebral column, composed of articulating vertebrae which are lightweight yet strong.
The ribs attach to the spine and there are no limbs or limb girdles. The main external features of the fish, the fins, are composed of either bony or soft spines called rays which, with the exception of the caudal fins, have no direct connection with the spine, they are supported by the muscles. The heart has two chambers and pumps the blood through the respiratory surfaces of the gills and on round the body in a single circulatory loop; the eyes have only local vision. There is an inner ear but no middle ear. Low frequency vibrations are detected by the lateral line system of sense organs that run along the length of the sides of fish, these respond to nearby movements and to changes in water pressure. Sharks and rays are basal fish with numerous primitive anatomical features similar to those of ancient fish, including skeletons composed of cartilage, their bodies tend to be dorso-ventrally flattened, they have five pairs of gill slits and a large mouth set on the underside of the head. The dermis is covered with separate dermal placoid scales.
They have a cloaca into which genital passages open, but not a swim bladder. Cartilaginous fish produce a small number of yolky eggs; some species are ovoviviparous and the young develop internally but others are oviparous and the larvae develop externally in egg cases. The bony fish lineage shows more derived anatomical traits with major evolutionary changes from the features of ancient fish, they have a bony skeleton, are laterally flattened, have five pairs of gills protected by an operculum, a mouth at or near the tip of the snout. The dermis is covered with overlapping scales. Bony fish have a swim bladder which helps them maintain a constant depth in the water column, but not a cloaca, they spawn a large number of small eggs with little yolk which they broadcast into the water column. In many respects fish anatomy is different from humans and mammals, yet it shares the same basic vertebrate body plan from which all vertebrates have evolved: a notochord, rudimentary vertebrae, a well-defined head and tail.
Fish have a variety of different body plans. At the broadest level their body is divided into head and tail, although the divisions are not always externally visible; the body is fusiform, a streamlined body plan found in fast-moving fish. They may be filiform or vermiform. Fish are either compressed or depressed. There are two different skeletal types: the exoskeleton, the stable outer shell of an organism, the endoskeleton, which forms the support structure inside the body; the skeleton of the fish is made of either bone. The main features of the fish, the fins, are bony fin rays and, except for the caudal fin, have no direct connection with the spine, they are supported only by the muscles. The ribs attach to the spine. Bones are rigid organs, they function to move and protect the various organs of the body, produce red and white blood cells and store minerals. Bone tissue is a type of dense connective tissue. Bones have a complex internal and external structure, they are lightweight, yet hard, in addition to fulfilling their many other functions.
Fish bones have been used to bioremediate lead from contaminated soil. Fish are vertebrates. All vertebrates are built along the basic chordate body plan: a stiff rod running through the length of the animal, with a hollow tube of nervous tissue above it and the gastrointestinal tract below. In all vertebrates, the mouth is found at, or right below, the anterior end of the animal, while the anus opens to the exterior before the end of the body; the remaining part of the body continuing aft of the anus forms a tail with vertebrae and spinal cord, but no gut. The defining characteristic of a vertebrate is the vertebral column, in which the notochord found in all chordates has been replaced by a segmented series of stiffer elements separated by mobile joints. However, a few fish have secondarily lost this anatomy, retaining the notochord into adulthood, such as the sturgeon; the vertebral column consists of a centrum, vertebral arches which protrude from the top and bottom of the centrum, various processes which pr
The three-spined stickleback is a fish native to most inland coastal waters north of 30°N. It has long been a subject of scientific study for many reasons, it shows great morphological variation throughout its range, ideal for questions about evolution and population genetics. Most populations are anadromous and tolerant of changes in salinity, a subject of interest to physiologists, it displays elaborate breeding behavior and it can be social making it a popular subject of enquiry in fish ethology and behavioral ecology. Its antipredator adaptations, host-parasite interactions, sensory physiology, reproductive physiology, endocrinology have been much studied. Facilitating these studies is the fact that the three-spined stickleback is easy to find in nature and easy to keep in aquaria; this species can reach lengths of 8 cm, but lengths of 3–4 centimetres at maturity are more common. The body is laterally compressed; the base of the tail is slender. The caudal fin has 12 rays; the dorsal fin has 10–14 rays.
The third spine is much shorter than the other two. The back of each spine is joined to the body by a thin membrane; the anal fin is preceded by a short spine. The pelvic fins consist of one ray. All spines can be locked in an erect position, making the fish hard to swallow by a predator; the pectoral fins are large, with 10 rays. The body bears no scales, but is protected by bony plates on the back and belly. Only one ventral plate is present, but the number of flank plates varies across the distribution range and across habitat types. Dorsal coloration varies, but tends towards a drab olive or a silvery green, sometimes with brown mottling; the flanks and belly are silvery. In males during the breeding season, the eyes become blue and the lower head and anterior belly turn bright red; the throat and belly of breeding females can turn pink. A few populations, have breeding males which are all black or all white; the three-spined stickleback is found only in the Northern Hemisphere, where it inhabits coastal waters or freshwater bodies.
It can live in either brackish, or salt water. It prefers slow-flowing water with areas of emerging vegetation, it can be found in ditches, lakes, quiet rivers, sheltered bays and harbours. In North America, it ranges along the East Coast from Chesapeake Bay to the southern half of Baffin Island and the western shore of Hudson Bay, along the West Coast from southern California to the western shore of Alaska and the Aleutian Islands, it can be found throughout Europe between 35 and 70°N. In Asia, the distribution stretches from the Korean peninsula to the Bering Straits, its distribution could be said to be circumpolar were it not for the fact that it is absent from the north coast of Siberia, the north coast of Alaska, the Arctic islands of Canada. Three subspecies are recognized by the IUCN: G. a. aculeatus is found in most of the species range, is the subspecies most termed the three-spined stickleback. G. a. williamsoni, the unarmored threespine stickleback, is found only in North America. These subspecies represent three examples from the enormous range of morphological variation present within three-spined sticklebacks.
These fall into the anadromous and the freshwater forms. The anadromous form spends most of its adult life eating plankton and fish in the sea, returns to freshwater to breed; the adult fish are between 6 and 10 cm long, have 30 to 40 lateral armour plates along their sides. They have long dorsal and pelvic spines; the anadromous form is morphologically similar all around the Northern Hemisphere, such that anadromous fish from the Baltic, the Atlantic and the Pacific all resemble each other quite closely. Three-spined stickleback populations are found in freshwater lakes and streams; these populations were formed when anadromous fish started spending their entire lifecycle in fresh water, thus evolved to live there all year round. Freshwater populations are morphologically diverse, to the extent that many observers would describe a new subspecies of three-spined stickleback in every lake in the Northern Hemisphere. One consistent difference between freshwater populations and their anadromous ancestors is the amount of body armour, as the majority of freshwater fish only have between none and 12 lateral armour plates, shorter dorsal and pelvic spines.
However large morphological differences occur between lakes. One major axis of variation is between populations found in deep, steep-sided lakes and those in small, shallow lakes; the fish in the deep lakes feed in the surface waters on plankton, have large eyes, with short, slim bodies and upturned jaws. Some researchers refer to this as the limnetic form. Fish from shallow lakes feed on the lake bed, are long and heavy bodied
Most bony fishes have two sets of jaws made of bone. The primary oral jaws open and close the mouth, a second set of pharyngeal jaws are positioned at the back of the throat; the oral jaws are used to manipulate prey by biting and crushing. The pharyngeal jaws, so-called because they are positioned within the pharynx, are used to further process the food and move it from the mouth to the stomach. Cartilaginous fishes, such as sharks and rays, have one set of oral jaws made of cartilage, they do not have pharyngeal jaws. Jaws are articulated and oppose vertically, comprising an upper jaw and a lower jaw and can bear numerous ordered teeth. Cartilaginous fishes grow multiple sets and replace teeth as they wear by moving new teeth laterally from the medial jaw surface in a conveyor-belt fashion. Teeth are replaced multiple times in most bony fishes, but unlike cartilaginous fishes, the new tooth erupts only after the old one has fallen out. Jaws originated in the pharyngeal arches supporting the gills of jawless fish.
The earliest jaws appeared is now extinct placoderms and spiny sharks during the Silurian, about 430 million years ago. The original selective advantage offered by the jaw was not related to feeding, but to increased respiration efficiency—the jaws were used in the buccal pump to pump water across the gills; the familiar use of jaws for feeding would have developed as a secondary function before becoming the primary function in many vertebrates. All vertebrate jaws, including the human jaw, evolved from early fish jaws; the appearance of the early vertebrate jaw has been described as "perhaps the most profound and radical evolutionary step in the vertebrate history". Fish without jaws had more difficulty surviving than fish with jaws, most jawless fish became extinct. Jaws use linkage mechanisms; these linkages can be common and complex in the head of bony fishes, such as wrasses, which have evolved many specialized feeding mechanisms. Advanced are the linkage mechanisms of jaw protrusion. For suction feeding a system of linked four-bar linkages is responsible for the coordinated opening of the mouth and the three-dimensional expansion of the buccal cavity.
Other linkages are responsible for protrusion of the premaxilla. Linkage systems are distributed in animals; the most thorough overview of the different types of linkages in animals has been provided by M. Muller, who designed a new classification system, well suited for biological systems; the skull of fishes is formed from a series of loosely connected bones. Lampreys and sharks only possess a cartilaginous endocranium, with both the upper and lower jaws being separate elements. Bony fishes have additional dermal bone, forming a more or less coherent skull roof in lungfish and holost fish; the lower jaw defines a chin. The simpler structure is found in jawless fish, in which the cranium is represented by a trough-like basket of cartilaginous elements only enclosing the brain, associated with the capsules for the inner ears and the single nostril. Distinctively, these fish have no jaws. Cartilaginous fish, such as sharks have simple skulls; the cranium is a single structure forming a case around the brain, enclosing the lower surface and the sides, but always at least open at the top as a large fontanelle.
The most anterior part of the cranium includes a forward plate of cartilage, the rostrum, capsules to enclose the olfactory organs. Behind these are the orbits, an additional pair of capsules enclosing the structure of the inner ear; the skull tapers towards the rear, where the foramen magnum lies above a single condyle, articulating with the first vertebra. There are, in addition, at various points throughout the cranium, smaller foramina for the cranial nerves; the jaws consist of separate hoops of cartilage always distinct from the cranium proper. In ray-finned fishes, there has been considerable modification from the primitive pattern; the roof of the skull is well formed, although the exact relationship of its bones to those of tetrapods is unclear, they are given similar names for convenience. Other elements of the skull, may be reduced; the upper jaw is formed from the premaxilla, with the maxilla itself located further back, an additional bone, the symplectic, linking the jaw to the rest of the cranium.
Although the skulls of fossil lobe-finned fish resemble those of the early tetrapods, the same cannot be said of those of the living lungfishes. The skull roof is not formed, consists of multiple, somewhat irregularly shaped bones with no direct relationship to those of tetrapods; the upper jaw is formed from the vomers alone, all of which bear teeth. Much of the skull is formed from cartilage, its overall structure is reduced. In vertebrates, the lower jaw is a bone forming the skull with the cranium. In lobe-finned fishes and the early fossil tetrapods, the bone homologous to the mandible of mammals is the largest of several bones in the lower jaw, it is referred to as the dentary bone, forms the body of the outer surface of the jaw. It is bordered below by a number of splenial bones, while the angle of the jaw is formed by a lower angular bone and a suprangular bone just above it; the inner surface of the jaw is lined by a prearticular bone, while the articular bone forms the articulation with the skull proper.
A set of three narrow coronoid bones lie above the prearticular bone. As the name implies, the majority of the teeth are attached to the dentary, but there are also teet
Fins are the most distinctive anatomical features of a fish. They are composed of bony spines or rays protruding from the body with skin covering them and joining them together, either in a webbed fashion, as seen in most bony fish, or similar to a flipper, as seen in sharks. Apart from the tail or caudal fin, fish fins have no direct connection with the spine and are supported only by muscles, their principal function is to help. Fins located in different places on the fish serve different purposes such as moving forward, keeping an upright position or stopping. Most fish use fins when swimming, flying fish use pectoral fins for gliding, frogfish use them for crawling. Fins can be used for other purposes. For every type of fin, there are a number of fish species in which this particular fin has been lost during evolution. Bony fishes form, they have skeletons made of bone, can be contrasted with cartilaginous fishes which have skeletons made of cartilage. Bony fishes are divided into lobe-finned fish.
Most fish are ray-finned, an diverse and abundant group consisting of over 30,000 species. It is the largest class of vertebrates in existence today. In the distant past, lobe-finned fish were abundant. Nowadays they are extinct, with only eight living species. Bony fish have fin rays called lepidotrichia, they have swim bladders, which allows the fish to create a neutral balance between sinking and floating without having to use its fins. However, swim bladders are absent in many fish, most notably in Lungfishes, which are the only fish to have retained the primitive lung present in the common ancestor of bony fish from which swim bladders evolved. Bony fishes have an operculum, which helps them breathe without having to use fins to swim. Lobe-finned fishes are a class of bony fishes called Sarcopterygii, they have fleshy, paired fins, which are joined to the body by a single bone. The fins of lobe-finned fish differ from those of all other fish in that each is borne on a fleshy, scaly stalk extending from the body.
Pectoral and pelvic fins have articulations resembling those of tetrapod limbs. These fins evolved into legs of the first tetrapod land vertebrates, amphibians, they possess two dorsal fins with separate bases, as opposed to the single dorsal fin of ray-finned fish. The coelacanth is a lobe-finned fish, still extant, it is thought to have evolved into its current form about 408 million years ago, during the early Devonian. Locomotion of the coelacanths is unique to their kind. To move around, coelacanths most take advantage of up or downwellings of the current and drift, they use their paired fins to stabilize their movement through the water. While on the ocean floor their paired fins are not used for any kind of movement. Coelacanths can create thrust for quick starts by using their caudal fins. Due to the high number of fins they possess, coelacanths have high maneuverability and can orient their bodies in any direction in the water, they have been seen swimming belly up. It is thought that their rostral organ helps give the coelacanth electroperception, which aids in their movement around obstacles.
Ray-finned fishes are a class of bony fishes called Actinopterygii. Their fins contain rays. A fin may contain only soft rays, or a combination of both. If both are present, the spiny rays are always anterior. Spines are stiff and sharp. Rays are soft, flexible and may be branched; this segmentation of rays is the main difference. Spines have a variety of uses. In catfish, they are used as a form of defense. Triggerfish use spines to lock themselves in crevices to prevent them being pulled out. Lepidotrichia are bony, bilaterally paired, segmented fin rays found in bony fishes, they develop around actinotrichia as part of the dermal exoskeleton. Lepidotrichia are composed of bone, but in early osteichthyans such as Cheirolepis, there was dentine and enamel, they appear as a series of disks stacked one on top of another. The genetic basis for the formation of the fin rays is thought to be genes coded for the production of certain proteins, it has been suggested that the evolution of the tetrapod limb from lobe-finned fishes is related to the loss of these proteins.
Cartilaginous fishes are a class of fishes called Chondrichthyes. They have skeletons made of cartilage rather than bone; the class includes sharks and chimaeras. Shark fin skeletons are elongated and supported with soft and unsegmented rays named ceratotrichia, filaments of elastic protein resembling the horny keratin in hair and feathers; the pectoral and pelvic girdles, which do not contain any dermal elements, did not connect. In forms, each pair of fins became ventrally connected in the middle when scapulocoracoid and pubioischiadic bars evolved. In rays, the pectoral fins have connected to the head and are flexible. One of the primary characteristics present in most sharks is the heterocercal tail, which aids in locomotion. Most sharks have eight fins. Sharks can only drift away from objects directly in front of them because
FishBase is a global species database of fish species. It is the most extensively accessed online database on adult finfish on the web. Over time it has "evolved into a dynamic and versatile ecological tool", cited in scholarly publications. FishBase provides comprehensive species data, including information on taxonomy, geographical distribution and morphology, behaviour and habitats and population dynamics as well as reproductive and genetic data. There is access to tools such as trophic pyramids, identification keys, biogeographical modelling and fishery statistics and there are direct species level links to information in other databases such as LarvalBase, GenBank, the IUCN Red List and the Catalog of Fishes; as of November 2018, FishBase included descriptions of 34,000 species and subspecies, 323,200 common names in 300 languages, 58,900 pictures, references to 55,300 works in the scientific literature. The site has about 700,000 unique visitors per month; the origins of FishBase go back to the 1970s, when the fisheries scientist Daniel Pauly found himself struggling to test a hypothesis on how the growing ability of fish was affected by the size of their gills.
Hypotheses, such as this one, could be tested only if large amounts of empirical data were available. At the time, fisheries management used analytical models which required estimates for fish growth and mortality, it can be difficult for fishery scientists and managers to get the information they need on the species that concern them, because the relevant facts can be scattered across and buried in numerous journal articles, reports and other sources. It can be difficult for people in developing countries who need such information. Pauly believed that the only practical way fisheries managers could access the volume of data they needed was to assemble and consolidate all the data available in the published literature into some central and accessed repository; such a database would be useful if the data has been standardised and validated. This would mean that when scientists or managers need to test a new hypothesis, the available data will be there in a validated and accessible form, there will be no need to create a new dataset and have to validate it.
Pauly recruited Rainer Froese, the beginnings of a software database along these lines was encoded in 1988. This database confined to tropical fish, became the prototype for FishBase. FishBase was subsequently extended to cover all finfish, was launched on the Web in August 1996, it is now the most accessed online database for fish in the world. In 1995 the first CD-ROM was released as "FishBase 100". Subsequent CDs have been released annually; the software runs on Microsoft Access. FishBase does not detail the early and juvenile stages of fish. In 1999 a complimentary database, called LarvalBase, went online under the supervision of Bernd Ueberschär, it covers ichthyoplankton and the juvenile stage of fishes, with detailed data on fish eggs and larvae, fish identification, as well as data relevant to the rearing of young fish in aquaculture. Given FishBase's success, there was a demand for a database covering forms of aquatic life other than finfish; this resulted, in the birth of SeaLifeBase. The long-term goal of SeaLifeBase is to develop an information system modelled on FishBase, but including all forms of aquatic life, both marine and freshwater, apart from the finfish which FishBase specialises in.
Altogether, there are about 300,000 known species in this category. As awareness of FishBase has grown among fish specialists, it has attracted over 2,310 contributors and collaborators. Since 2000 FishBase has been supervised by a consortium of nine international institutions. To date, the FishBase consortium has grown to twelve members; the GEOMAR - Helmholtz Centre for Ocean Research for Ocean Research Kiel in Germany, functions as the coordinating body. Catalog of Fishes List of online encyclopedias Bailly N Why there may be discrepancies in the assessment of scientific names between the Catalog of Fishes and FishBase Version 2, 6 May 2010. Bailly N, Reyes Jr R, Atanacio R and Froese R "Simple Identification Tools in FishBase" In: Nimis PL and Vignes Lebbe R. Tools for Identifying Biodiversity: Progress and Problems, pages 31–36. ISBN 978-88-8303-295-0. Christensen V, CJ Walters, R Ahrens, J Alder, J Buszowski, LB Christensen, WWL Cheung, J Dunne, R Froese, V Karpouzi, K Kaschner, K Kearney, S Lai, V Lam, MLD Palomares, A Peters-Mason, C Piroddia, JL Sarmiento, J Steenbeek, R Sumaila, R Watson, D Zeller and D Pauly Database-driven models of the world's Large Marine Ecosystems Ecological Modelling, 220: 1984–1996.
Froese R "The science in Fishbase" In: Villy Christensen and Jay Maclean Ecosystem Approaches to Fisheries: A Global Perspective, Cambridge University Press, pages 47–54. ISBN 978-0-521-13022-6. Froese R and Pauly D FishBase 2000: concepts and data sources ICLARM, Philippines. Froese R and Pauly D "Fishbase as a tool for comparing the life history patterns of flatfish" Netherlands Journal of Sea Research, 32: 235–239. Nauen CE A public electronic archive on the world’s fishes in support of sustainable fisheries CTA/Commonwealth Secretariat Seminar, Expert Meeting on ACP-EU Fisheries Relations, Brussels. Palomares, M. L. D. N. Bailly and D. Pauly FishBase, SeaLifeBase and database-driven ecosystem modeling p. 156-158. In: M. L. D. Palomares, L. Morissette, A. Cisnero-Montemayor, D. Varkey, M. Coll and C. Piroddi Ecopath 25 Years Conference Proceedings: Extended Abstracts. UBC Fisheries Centre Resear
Ganoine or ganoin is a glassy multi-layered mineralized tissue that covers the scales, cranial bones and fin rays in some non-teleost ray-finned fishes, such as gars and coelacanths. It is composed of rod-like, pseudoprismatic apatite crystallites, with less than 5% of organic matter. Existing fish groups featuring ganoin are bichirs and gars, but ganoin is characteristic of several extinct taxa, it is a characteristic component of ganoid scales. Ganoine is an ancient feature of ray-finned fishes, being found for example on the scales of stem group actinopteryigian Cheirolepis. While considered a synapomorphic character of ray-finned fishes, ganoine or ganoine-like tissues are found on the extinct acanthodii, it has been suggested that ganoine is homologous to tooth enamel in vertebrates or considered a type of enamel. Ganoine indeed contains amelogenin-like proteins and has a mineral content similar to that of tetrapod tooth enamel
The hyomandibula referred to as hyomandibular is a set of bones, found in the hyoid region in most fishes. It plays a role in suspending the jaws and/or operculum, it is suggested that in tetrapods, the hyomandibula evolved into the columella. In jawless fishes a series of gills opened behind the mouth, these gills became supported by cartilaginous elements; the first set of these elements surrounded the mouth to form the jaw. There are ample evidences; the upper portion of the second embryonic arch supporting the gill became the hyomandibular bone of jawed fishes, which supports the skull and therefore links the jaw to the cranium. When vertebrates found their way onto land, the hyomandibula, with its location near the ear, began to function as a sound amplifier beside its function to support the skull; as evolution attached the cranium of terrestrial vertebrates to the rest of the skull, the hyomandibula lost its supportive function and became an interior organ, the stapes, thus its secondary function had become its primary function.
Fish anatomy Palatoquadrate Kardong, Kenneth V. Vertebrates Comparative Anatomy, Evolution. Pp. 227, 693. "Hyomandibula". ZipcodeZoo.com. Archived from the original on 14 March 2012. Retrieved 30 January 2010. Gilbert, Scott F.. "The anatomical tradition: Evolutionary Embryology: Embryonic homologies". Developmental Biology. Sunderland: Sinauer Associates, Inc.. Retrieved 2018-04-09. Gilbert. Figure 1.14. Jaw structure in the fish and mammal