Fish anatomy

thumb|right|The red gills of this common carp are visibly exposed as a result of a gill flap [[birth defect.]] A gill () is a specialized respiratory organ that many aquatic animals use for aquatic gas exchange, i.e. to extract dissolved oxygen from water and to excrete carbon dioxide. Branchia (: branchiae, from Ancient Greek ) is the zoologists' academic name for gills.

bony skin-covered spines or rays protruding from the body of a fish or aquatic mammal

gas-filled organ that contributes to the ability of a fish to control its buoyancy

An otolith (, ' ear + , ', a stone), also called otoconium, statolith, or statoconium, is a calcium carbonate structure in the saccule or utricle of the inner ear, specifically in the vestibular system of vertebrates. The saccule and utricle, in turn, together make the otolith organs. These organs are what allows an organism, including humans, to perceive linear acceleration, both horizontally and vertically (gravity). They have been identified in both extinct and extant vertebrates.

thumb|Ovipositor of Tettigoniidae|long-horned grasshopper (the two cerci are also visible)

thumb|300px|right|The elongate jewel squid (Histioteuthis reversa), so called because the photophores festooning its body make it appear bejewelled. thumb|300px|right|Diagram of a cephalopod's photophore, in vertical section.

bones in a fish that provide facial support structure and a protective covering for the gills

organ possessed by electric fish

sensory structure present in sharks

whisker-like sensory organs near the mouth of some fish species

study of the form or morphology of fishes

anatomical structure that connects the swim bladder to the auditory system in fishes

thumb|The claspers of a spotted wobbegong shark (Orectolobus maculatus) thumb|The claspers of a young spinner shark (Carcharhinus brevipinna) thumb|Life restoration of the extinct chimaera Ischyodus, showing the presence of a cephalic clasper on the head of males (as well as a pelvic clasper) but absent in females In biology, a clasper is a male anatomical structure found in some groups of animals, used in mating. thumb|300x300px|A close up view of a chimaera clasper (Hydrolagus collie). Note the many small tooth-like projections covering the exterior surface. thumb|Illustration of Harpagofut

part of a fish

small rigid plate that grows out of the skin of a fish

The hepatopancreas, digestive gland or midgut gland is an organ of the digestive tract of arthropods and molluscs. It provides the functions which in mammals are provided separately by the liver and pancreas, including the production of digestive enzymes, and absorption of digested food.

bony skeleton of fish

bony or cartilaginous processes that project from the branchial arch

teeth of a shark

mophological feature in some fish

measurement of various fish characteristics such as length and weight

individual opening to a gill

bony "loops" present in fish, which support the gills

thumb|right|The ductus pneumaticus from the gas bladder to the gut in a [[common rudd.]] Physostomes are fishes that have a pneumatic duct connecting the gas bladder to the alimentary canal. This allows the gas bladder to be filled or emptied via the mouth. This not only allows the fish to fill their bladder by gulping air, but also to rapidly ascend in the water without the bladder expanding to bursting point. In contrast, fish without any connection to their gas bladder are called physoclisti.

teeth in the pharyngeal arch of the throat of cyprinids, suckers, and a number of other fish species otherwise lacking teeth

thumb|Skeletal head of an Bowfin|Amia calva. Hyamandibular marked h, top image, upper right corner The hyomandibula, commonly referred to as hyomandibular [bone] (, from , "upsilon-shaped" (υ), and Latin: mandibula, "jawbone"), is a set of bones that is found in the hyoid region in most fishes. It usually plays a role in suspending the jaws and/or operculum (teleostomi only). It is commonly suggested that in tetrapods (land animals), the hyomandibula evolved into the columella (stapes).

part of a shark intestine

thumb|300px|Nile crocodile (Crocodylus niloticus) A polyphyodont is any animal whose teeth are continually replaced. In contrast, diphyodonts are characterized by having only two successive sets of teeth.

thumb|250px|The glassy appearance of the scales of this spotted gar is due to ganoine. thumb|The mineral texture of alligator gar scales consists of bundles of cross-plied hydroxyapatite minerals oriented towards the scale's surface. Ganoine or ganoin is a glassy, often multi-layered mineralized tissue that covers the scales, cranial bones and fin rays in some non-teleost ray-finned fishes, such as gars and bichirs, as well as lobe-finned coelacanths. It is composed of rod-like, pseudoprismatic apatite crystallites, with less than 5% of organic matter. Existing fish groups featuring ganoin are

Physoclisti are, collectively, fishes that lack a connection between the gas bladder and the alimentary canal, with the bladder serving only as a buoyancy organ.

Cosmine is a spongy, bony material that makes up the dentine-like layers in the scales of the lobe-finned fishes of the class Sarcopterygii. Fish scales that include layers of cosmine are known as cosmoid scales.

organ that allows fish to breathe underwater

part of the arthropod and insect central nervous system

Meristics is an area of zoology and botany which relates to counting quantitative features of animals and plants, such as the number of fins or scales in fish. A meristic (countable trait) can be used to describe a particular species, or used to identify an unknown species. Meristic traits are often described in a shorthand notation called a meristic formula.

part of the circulatory system of fish

A kinocilium is a special type of cilium on the apex of hair cells located in the sensory epithelium of the vertebrate inner ear. Contrasting with stereocilia, which are numerous, there is only one kinocilium on each hair cell. The kinocilium can be identified by its apical position as well as its enlarged tip.

Structure found in some sharks and rays