Editing Teleost (section)

== Physiology ==

{{Further|Fish physiology}}

=== Respiration ===

[[File:Gills.jpg|thumb|Gills]]

{{Further|Fish respiration|Fish gill}}

The major means of respiration in teleosts, as in most other fish, is the transfer of gases over the surface of the gills as water is drawn in through the mouth and pumped out through the gills. Apart from the [[swim bladder]], which contains a small amount of air, the body does not have oxygen reserves, and respiration needs to be continuous over the fish's life. Some teleosts exploit habitats where the oxygen availability is low, such as stagnant water or wet mud; they have developed accessory tissues and organs to support gas exchange in these habitats.<ref name=Physiology>{{cite book |last=Meurant |first=Gerard |title=Fish Physiology V10A |url=https://books.google.com/books?id=yINDnV4mWi8C&pg=PA263 |year=1984 |publisher=[[Academic Press]] |isbn=978-0-08-058531-4 |pages=263–}}</ref>

Several genera of teleosts have independently developed air-breathing capabilities, and some have become [[amphibious fish|amphibious]]. Some [[Combtooth blenny|combtooth blennies]] emerge to feed on land, and freshwater eels are able to absorb oxygen through damp skin. [[Mudskipper]]s can remain out of water for considerable periods, exchanging gases through skin and [[mucous membrane]]s in the mouth and pharynx. [[Swamp eel]]s have similar well-vascularised mouth-linings, and can remain out of water for days and go into a resting state ([[aestivation]]) in mud.<ref>{{cite book |editor1=Paxton, J.R. |editor2=Eschmeyer, W.N. |author=Liem, Karel F. |year=1998 |title=Encyclopedia of Fishes |publisher=Academic Press |pages=173–174 |isbn=978-0-12-547665-2}}</ref> The [[Anabantoidei|anabantoids]] have developed an accessory breathing structure known as the [[Anabantoidei#Labyrinth organ|labyrinth organ]] on the first gill arch and this is used for respiration in air, and [[airbreathing catfish]] have a similar suprabranchial organ. Certain other catfish, such as the [[Loricariidae]], are able to respire through air held in their digestive tracts.<ref>{{cite journal |last=Armbruster |first=Jonathan W. |url=http://www.auburn.edu/academic/science_math/res_area/loricariid/fish_key/Air.pdf |title=Modifications of the digestive tract for holding air in loricariid and scoloplacid catfishes |journal=Copeia |year=1998 |issue=3 |pages=663–675 |doi=10.2307/1447796 |volume=1998 |jstor=1447796}}</ref>

=== Sensory systems ===

[[File:Gasterosteus aculeatus with stained neuromasts.png|thumb|A stickleback stained to show the [[lateral line system|lateral line]] elements (neuromasts)]]

{{Further|Sensory systems in fish|Electroreception|Magnetoreception}}

Teleosts possess highly developed sensory organs. Nearly all daylight [[vision in fishes|fish have colour vision]] at least as good as a normal human's. Many fish also have [[chemoreceptor]]s responsible for acute senses of taste and smell. Most fish have sensitive receptors that form the [[lateral line system]], which detects gentle currents and vibrations, and senses the motion of nearby fish and prey.<ref name="Encarta 99">{{cite book |last=Orr |first=James |year=1999 |title=Fish |publisher=[[Encarta|Microsoft Encarta 99]] |isbn=978-0-8114-2346-5 |url-access=registration |url=https://archive.org/details/fearsomefishcree00stev}}</ref> Fish sense sounds in a variety of ways, using the lateral line, the swim bladder, and in some species the Weberian apparatus. Fish orient themselves using landmarks, and may use [[mental map]]s based on multiple landmarks or symbols. Experiments with mazes show that fish possess the [[spatial memory]] needed to make such a mental map.<ref>{{cite web |url=http://juls.sa.utoronto.ca/Issues/JULS-Vol2Iss1/JULS-Vol2Iss1-Review3.pdf |archive-url=https://web.archive.org/web/20110706211428/http://juls.sa.utoronto.ca/Issues/JULS-Vol2Iss1/JULS-Vol2Iss1-Review3.pdf |archive-date=6 July 2011 |title=Appropriate maze methodology to study learning in fish |author=Journal of Undergraduate Life Sciences |access-date=28 May 2009 |url-status=dead}}</ref>

=== Osmoregulation ===

[[File:Rostrata.jpg|thumb|[[Osmosis|Osmotic]] challenge: [[American eel]]s spawn in the [[sea]] but spend most of their adult life in [[freshwater]], returning only to spawn.]]

The skin of a teleost is largely impermeable to water, and the main interface between the fish's body and its surroundings is the gills. In freshwater, teleost fish gain water across their gills by [[osmosis]], while in seawater they lose it. Similarly, salts [[diffusion|diffuse]] outwards across the gills in freshwater and inwards in salt water. The [[European flounder]] spends most of its life in the sea but often migrates into estuaries and rivers. In the sea in one hour, it can gain Na<sup>+</sup> ions equivalent to forty percent of its total free [[sodium]] content, with 75 percent of this entering through the gills and the remainder through drinking. By contrast, in rivers there is an exchange of just two percent of the body Na<sup>+</sup> content per hour. As well as being able to selectively limit salt and water exchanged by diffusion, there is an active mechanism across the gills for the elimination of salt in sea water and its uptake in fresh water.<ref name=Bentley>{{cite book |author=Bentley, P.J. |title=Endocrines and Osmoregulation: A Comparative Account in Vertebrates |url=https://books.google.com/books?id=U0D3BwAAQBAJ&pg=PA26 |year=2013 |publisher=[[Springer Publishing|Springer]] |isbn=978-3-662-05014-9|page=26}}</ref>

=== Thermoregulation ===

Fish are [[poikilothermy|cold-blooded]], and in general their body temperature is the same as that of their surroundings. They gain and lose heat through their skin, and regulate their circulation in response to changes in water temperature by increasing or reducing the blood flow to the gills. Metabolic heat generated in the muscles or gut is quickly dissipated through the gills, with blood being diverted away from the gills during exposure to cold.<ref name=Whittow>{{cite book |last=Whittow |first=G. Causey |title=Comparative Physiology of Thermoregulation: Special Aspects of Thermoregulation |url=https://books.google.com/books?id=e5qjAgAAQBAJ&pg=PA223 |year=2013 |publisher=Academic Press |isbn=978-1-4832-5743-3 |page=223}}</ref> Because of their relative inability to control their blood temperature, most teleosts can only survive in a small range of water temperatures.<ref>{{cite web |url=http://www.aquarticles.com/articles/breeding/McFarlane_Warm_Blooded_Fish.html |title=Warm-blooded fish |author=McFarlane, Paul |date=1 January 1999 |work=Monthly Bulletin |publisher=Hamilton and District Aquarium Society |access-date=6 January 2016 |url-status=dead |archive-url=https://web.archive.org/web/20130515103309/http://www.aquarticles.com/articles/breeding/McFarlane_Warm_Blooded_Fish.html |archive-date=15 May 2013 |df=dmy-all}}</ref>

Teleost species that inhabit colder waters have a higher proportion of unsaturated fatty acids in brain cell membranes compared to fish from warmer waters, which allows them to maintain appropriate [[membrane fluidity]] in the environments in which they live.<ref>{{cite journal |last1=Logue |first1=J. A. |last2=Vries |first2=A. L. de |last3=Fodor |first3=E. |last4=Cossins |first4=A. R. |date=2000-07-15 |title=Lipid compositional correlates of temperature-adaptive interspecific differences in membrane physical structure |url=https://jeb.biologists.org/content/203/14/2105 |journal=Journal of Experimental Biology |volume=203 |issue=14 |pages=2105–2115 |doi=10.1242/jeb.203.14.2105 |pmid=10862723|url-access=subscription }}</ref> When cold acclimated, teleost fish show physiological changes in skeletal muscle that include increased mitochondrial and capillary density.<ref>{{cite journal |last1=Johnston |first1=I. A. |last2=Dunn |first2=J. |date=1987 |title=Temperature acclimation and metabolism in ectotherms with particular reference to teleost fish |url=https://pubmed.ncbi.nlm.nih.gov/3332497/ |journal=Symposia of the Society for Experimental Biology |volume=41 |pages=67–93 |pmid=3332497}}</ref> This reduces diffusion distances and aids in the production of aerobic [[Adenosine triphosphate|ATP]], which helps to compensate for the drop in [[metabolic rate]] associated with colder temperatures.

[[Tuna]] and other [[animal locomotion|fast-swimming]] [[Pelagic zone|ocean-going]] fish maintain their muscles at higher temperatures than their environment for efficient locomotion.<ref name=Martin>{{cite web |url=http://elasmo-research.org/education/topics/p_warm_body_1.htm |title=Fire in the Belly of the Beast |last=Martin |first=R. Aidan |date=April 1992 |publisher=ReefQuest Centre for Shark Research|access-date=6 January 2016}}</ref> Tuna achieve muscle temperatures {{convert|19|F-change|order=flip}} or even higher above the surroundings by having a [[countercurrent exchange|counterflow system]] in which the [[metabolism|metabolic heat]] produced by the muscles and present in the venous blood, pre-warms the arterial blood before it reaches the muscles. Other adaptations<!--off thermoregulation topic?--> of tuna for speed include a streamlined, spindle-shaped body, fins designed to reduce [[drag (physics)|drag]],<ref name=Martin/> and muscles with a raised [[myoglobin]] content, which gives these a reddish colour and makes for a more efficient use of oxygen.<ref>{{cite journal |author=Brown, W. Duane |year=1962 |title=The concentration of myoglobin and hemoglobin in tuna flesh |journal=[[Journal of Food Science]] |volume=27 |issue=1 |pages=26–28 |doi=10.1111/j.1365-2621.1962.tb00052.x}}</ref> In [[polar seas|polar regions]] and in the [[deep sea fish|deep ocean]], where the temperature is a few degrees above freezing point, some large fish, such as the [[swordfish]], [[marlin]] and tuna, have a heating mechanism which raises the temperature of the brain and eye, allowing them significantly better vision than their cold-blooded prey.<ref>{{cite news |url=https://www.uq.edu.au/news/article/2005/01/warm-eyes-give-deep-sea-predators-super-vision |title=Warm eyes give deep-sea predators super vision |last=Fritsches |first=Kerstin |date=11 January 2005 |publisher=University of Queensland |access-date=6 January 2016}}</ref>

=== Buoyancy ===

[[File:Swim bladder.jpg|thumb|right|A teleost [[swim bladder]]]]

The body of a teleost is denser than water, so fish must compensate for the difference, or they will sink. A defining feature of [[Actinopteri]] (Chondrostei, Holostei and teleosts) is the [[swim bladder]].<ref>{{cite journal | doi=10.1038/srep30580 | title=Molecular developmental mechanism in polypterid fish provides insight into the origin of vertebrate lungs | date=2016 |last1=Tatsumi |first1=Norifumi |last2=Kobayashi |first2=Ritsuko |last3=Yano |first3=Tohru |last4=Noda |first4=Masatsugu |last5=Fujimura |first5=Koji |last6=Okada |first6=Norihiro |last7=Okabe |first7=Masataka | journal=Scientific Reports | volume=6 | page=30580 | pmid=27466206 | pmc=4964569 | bibcode=2016NatSR...630580T }}</ref><ref>{{cite journal | pmc=8013215 | date=2020 |last1=Funk |first1=E. C. |last2=Breen |first2=C. |last3=Sanketi |first3=B. D. |last4=Kurpios |first4=N. |last5=McCune |first5=A. |title=Changes in Nkx2.1, Sox2, Bmp4, and Bmp16 expression underlying the lung-to-gas bladder evolutionary transition in ray-finned fishes |journal=Evolution & Development |volume=22 |issue=5 |pages=384–402 |doi=10.1111/ede.12354 |pmid=33463017}}</ref> Originally present in the last common ancestor of the teleosts, it has since been lost independently at least 30–32 times in at least 79 of 425 families of teleosts where the swim bladder is absent in one or more species. This absence is often the case in fast-swimming fishes such as the tuna and [[mackerel]].<ref>{{cite journal |url=https://onlinelibrary.wiley.com/doi/10.1111/j.1525-142X.2004.04030.x |doi=10.1111/j.1525-142X.2004.04030.x |title=Twenty ways to lose your bladder: Common natural mutants in zebrafish and widespread convergence of swim bladder loss among teleost fishes |date=2004 |last1=McCune |first1=Amy R. |last2=Carlson |first2=Rose L. |journal=Evolution & Development |volume=6 |issue=4 |pages=246–259 |url-access=subscription }}</ref> The swim bladder helps fish adjusting their buoyancy through manipulation of gases, which allows them to stay at the current water depth, or ascend or descend without having to waste energy in swimming. In the more primitive groups like some [[Leuciscinae|minnows]], the swim bladder is open (physostomous) to the [[esophagus]]. In fish where the swim bladder is closed (physoclistous), the gas content is controlled through the [[rete mirabilis]], a network of blood vessels serving as a countercurrent gas exchanger between the swim bladder and the blood.<ref>{{cite book |last=Kardong |first=K. |year=2008 |title=Vertebrates: Comparative anatomy, function, evolution |edition=5th |location=Boston |publisher=McGraw-Hill |isbn=978-0-07-304058-5 }}</ref>

=== Locomotion ===

[[File:Pink-wing flying fish.jpg|thumb|[[Flying fish]] combine swimming movements with the ability to [[gliding flight|glide]] in air using their long [[pectoral fin]]s.]]

{{Main|Fish locomotion}}

A typical teleost fish has a streamlined body for rapid swimming, and locomotion is generally provided by a lateral undulation of the hindmost part of the trunk and the tail, propelling the fish through the water.<ref>{{cite book |title=Numerical Studies of Hydrodynamics of Fish Locomotion and Schooling by a Vortex Particle Method |url=https://books.google.com/books?id=XXUiJb9ru7gC&pg=PA1 |year=2008 |isbn=978-1-109-14490-1 |pages=1–4}}</ref> There are many exceptions to this method of locomotion, especially where speed is not the main objective; among rocks and on [[coral reef]]s, slow swimming with great manoeuvrability may be a desirable attribute.<ref name=Kapoor>{{cite book |author1=Kapoor, B.G. |author2=Khanna, Bhavna |title=Ichthyology Handbook |url=https://books.google.com/books?id=I7WhoPBdAooC&pg=PA149 |year=2004 |publisher=Springer |isbn=978-3-540-42854-1 |pages=149–151}}</ref> Eels locomote by wiggling their entire bodies. Living among [[seagrass]]es and [[algae]], the [[seahorse]] adopts an upright posture and moves by fluttering its pectoral fins, and the closely related [[pipefish]] moves by rippling its elongated dorsal fin. [[Goby|Gobies]] "hop" along the substrate, propping themselves up and propelling themselves with their pectoral fins.<ref name=Patzner/> Mudskippers move in much the same way on terrestrial ground.<ref>{{cite journal |author=Pace, C. M. |author2=Gibb A. C. |title=Mudskipper pectoral fin kinematics in aquatic and terrestrial environments |journal=The Journal of Experimental Biology |volume=212|issue=Pt 14 |year=2009 |pages=2279–2286 |doi=10.1242/jeb.029041 |pmid=19561218 |doi-access=free}}</ref> In some species, a pelvic sucker allows them to climb, and the [[Hawaiian freshwater goby]] climbs waterfalls while migrating.<ref name=Patzner>{{cite book |author1=Patzner, Robert |author2=Van Tassell, James L. |author3=Kovacic, Marcelo |author4=Kapoor, B.G. |title=The Biology of Gobies |url=https://books.google.com/books?id=M_HRBQAAQBAJ&pg=PA261 |year=2011 |publisher=CRC Press |isbn=978-1-4398-6233-9 |pages=261, 507}}</ref> [[Tub gurnard|Gurnards]] have three pairs of free rays on their [[pectoral fin]]s which have a sensory function but on which they can walk along the substrate.<ref>{{cite journal |last1=Jamon |first1=M. |author2=Renous, S. |author3=Gasc, J.P. |author4=Bels, V. |author5=Davenport, J. |year=2007 |title=Evidence of force exchanges during the six-legged walking of the bottom-dwelling fish, ''Chelidonichthys lucerna'' |journal=[[Journal of Experimental Zoology]]|volume=307|issue=9 |pages=542–547 |doi=10.1002/jez.401| pmid=17620306|doi-access=free }}</ref> [[Flying fish]] launch themselves into the air and can [[gliding flight|glide]] on their enlarged pectoral fins for hundreds of metres.<ref>{{cite journal |author1=Dasilao, J.C. |author2=Sasaki, K. |year=1998 |title=Phylogeny of the flyingfish family Exocoetidae (Teleostei, Beloniformes) |journal=Ichthyological Research |volume=45|issue=4 |pages=347–353 |doi=10.1007/BF02725187 |bibcode=1998IchtR..45..347D |s2cid=24966029 }}</ref>

=== Sound production ===

The ability to produce sound for communication appears to have [[Convergent evolution|evolved independently]] in several teleost lineages.<ref>{{cite journal |last1=Rice |first1=A. N. |display-authors=etal |year=2022 |title=Evolutionary Patterns in Sound Production across Fishes |journal=Ichthyology & Herpetology |volume=110 |issue=1 |pages=1–12 |doi=10.1643/i2020172 |s2cid=245914602 |doi-access=free }}</ref> Sounds are produced either by [[stridulation]] or by vibrating the swim bladder. In the [[Sciaenidae]], the muscles that attach to the swim bladder cause it to oscillate rapidly, creating drumming sounds. Marine catfishes, sea horses and [[Haemulidae|grunts]] stridulate by rubbing together skeletal parts, teeth or spines. In these fish, the swim bladder may act as a [[acoustic resonance|resonator]]. Stridulation sounds are predominantly from 1000–4000 [[Hertz|Hz]], though sounds modified by the swim bladder have frequencies lower than 1000&nbsp;Hz.<ref>{{cite web |title=How do fish produce sounds? |website=Discovery of Sound in the Sea |url=http://www.dosits.org/animals/soundproduction/fishproduce/ |access-date=17 February 2017 |url-status=dead |archive-url=https://web.archive.org/web/20170215144728/http://www.dosits.org/animals/soundproduction/fishproduce/ |archive-date=15 February 2017 |df=dmy-all}}</ref><ref>{{cite web |last=Lobel |first=P. S. |title=Fish Courtship and Mating Sounds |publisher=Massachusetts Institute of Technology |url=http://seagrant.mit.edu/cfer/acoustics/exsum/lobel/extended1.html |access-date=17 February 2017 |archive-date=10 January 2018 |archive-url=https://web.archive.org/web/20180110032035/http://seagrant.mit.edu/cfer/acoustics/exsum/lobel/extended1.html |url-status=dead }}</ref>