Editing Cetacea (section)

== Physiology ==

=== Circulation ===
Cetaceans have powerful hearts. Blood oxygen is distributed effectively throughout the body. They are warm-blooded, i.e., they hold a nearly constant body temperature.<ref>{{cite web |title=Whales, dolphins and porpoises |url=https://www.dcceew.gov.au/environment/marine/marine-species/cetaceans |website=Department of Climate Change, Energy, the Environment and Water |publisher=Australian Government Department of Climate Change, Energy, the Environment and Water |access-date=19 October 2024}}</ref>

=== Respiration ===
{{unreferenced section|date=April 2018}}

Cetaceans have lungs, meaning they breathe air. An individual can last without a breath from a few minutes to over two hours depending on the species. Cetacea are deliberate breathers who must be awake to inhale and exhale. When stale air, warmed from the lungs, is exhaled, it condenses as it meets colder external air. As with a terrestrial mammal breathing out on a cold day, a small cloud of 'steam' appears. This is called the 'spout' and varies across species in shape, angle and height. Species can be identified at a distance using this characteristic.

The structure of the [[respiratory system|respiratory]] and [[circulatory system]]s is of particular importance for the life of [[marine mammals]]. The oxygen balance is effective. Each breath can replace up to 90% of the total lung volume. For land mammals, in comparison, this value is usually about 15%. During inhalation, about twice as much oxygen is absorbed by the lung tissue as in a land mammal. As with all mammals, the oxygen is stored in the blood and the lungs, but in cetaceans, it is also stored in various tissues, mainly in the muscles. The muscle pigment, [[myoglobin]], provides an effective bond. This additional oxygen storage is vital for deep diving, since beyond a depth around {{convert|100|m|ft|abbr=on}}, the lung tissue is almost completely compressed by the water pressure.

=== Abdominal organs ===
The stomach consists of three chambers. The first region is formed by a loose gland and a muscular forestomach (missing in beaked whales); this is followed by the main stomach and the [[pylorus]]. Both are equipped with glands to help digestion. A bowel adjoins the stomachs, whose individual sections can only be distinguished [[Histology|histologically]]. The [[liver]] is large and separate from the [[gall bladder]].<ref>{{cite book|author1=C. Edward Stevens|author2=Ian D. Hume|title=Comparative Physiology of the Vertebrate Digestive System|publisher=University of Cambridge|year=1995|access-date=5 September 2015|page=51|isbn=978-0-521-44418-7|url= https://books.google.com/books?id=DZuAsci2apAC&q=cetacean+digestive+system&pg=PR15}}</ref>

The kidneys are long and flattened. The salt concentration in cetacean blood is lower than that in seawater, requiring kidneys to excrete salt. This allows the animals to drink seawater.<ref>{{cite journal|author=Clifford A. Hui|title=Seawater Consumption and Water Flux in the Common Dolphin ''Delphinus delphis''|journal=Chicago Journals|volume=54|issue=4|pages=430–440|year=1981|jstor= 30155836}}</ref> The [[urinary bladder]] is proportionally smaller in cetaceans than in land mammals.<ref name="Hunter2015">{{cite book|url=https://books.google.com/books?id=TNAIBwAAQBAJ&pg=PR35|title=The Works of John Hunter, F.R.S.|date=26 March 2015|publisher=Cambridge University|isbn=978-1-108-07960-0|page=35|author=John Hunter}}</ref> The [[testicles|testes]] are located internally, without an external [[scrotum]].<ref name="WürsigThewissen2017">{{cite book|author1=Bernd Würsig|author2=J.G.M. Thewissen|author3=Kit M. Kovacs|title=Encyclopedia of Marine Mammals|url=https://books.google.com/books?id=T3zGDgAAQBAJ&q=testes+OR+testis+OR+testicles|date=27 November 2017|publisher=Elsevier Science|isbn=978-0-12-804381-3|access-date=19 October 2020|archive-date=29 June 2023|archive-url=https://web.archive.org/web/20230629161516/https://books.google.com/books?id=T3zGDgAAQBAJ&q=testes+OR+testis+OR+testicles|url-status=live}}</ref><ref name="rommel2007">{{cite book | last1 = Rommel | first1 = S.A. | first2 = D.A. | last2 = Pabst | first3 = W.A. | last3 = McLellan | chapter = Functional anatomy of the cetacean reproductive system, with comparisons to the domestic dog | title = Reproductive Biology and Phylogeny of Cetacea: Whales, Porpoises and Dolphins | date = 2007 | pages = 127–145 | editor-last = Miller | editor-first = D.L. | chapter-url = https://www.researchgate.net/publication/286334625 | doi = 10.1201/b11001| isbn = 9780429063626 }}</ref><ref name="rommel1998">{{cite magazine | last1 = Rommel | first1 = S.A. | first2 = D.A. | last2 = Pabst | first3 = W.A. | last3 = McLellan | title = Reproductive Thermoregulation in Marine Mammals | journal = American Scientist | volume = 86 | number = 5 | date = 1998 | pages = 440–448 | jstor = 27857097 | url = https://uncw.edu/mmsp/documents/rommeletal1998reproductivethermoregulation.pdf | url-status = live | archive-date = 22 November 2021 | archive-url = https://web.archive.org/web/20211122202231/https://uncw.edu/mmsp/documents/rommeletal1998reproductivethermoregulation.pdf}}</ref><ref name="Pabst, D. Ann 1998">{{cite book | last1 = Pabst | first1 = D.A. | last2 = Sentiel | first2 = A.R | first3 = W.A. | last3 = McLellan | chapter = Evolution of thermoregulatory function in cetacean reproductive systems | title = The Emergence of Whales | publisher = Springer US | date = 1998 | pages = 379–397 | series = Advances in Vertebrate Paleobiology | doi = 10.1007/978-1-4899-0159-0_13 | isbn = 978-1-4899-0161-3 | editor-last = Thewissen | editor-first = J.G.M.}}</ref> The uterus is [[Uterus#Other animals|bicornuate]].<ref name="rommel2007"/>

=== Senses ===
====Vision====
{{see also|Monochromacy}}
Cetacean eyes are set on the sides rather than the front of the head. This means only species with pointed 'beaks' (such as dolphins) have good [[binocular vision]] forward and downward. [[Lacrimal gland|Tear glands]] secrete greasy tears, which protect the eyes from the salt in the water. The lens is almost spherical, which is most efficient at focusing the minimal light that reaches deep water.{{citation needed|date=February 2025}}{{clarify|the shape is necessary for focusing in water and has little to do with light levels. monochromacy is because the light is monochrome blue at depth|date=February 2025}}

====Chemical senses====
Odontocetes have little to no ability to taste or smell, while mysticetes are believed to have some ability to smell because of their reduced, but functional [[olfactory system]].<ref>{{Cite journal|last1=Godfrey|first1=Stephen J.|last2=Geisler|first2=Jonathan|last3=Fitzgerald|first3=Erich M. G.|date=2013|title=On the Olfactory Anatomy in an Archaic Whale (Protocetidae, Cetacea) and the Minke Whale Balaenoptera acutorostrata (Balaenopteridae, Cetacea)|journal=The Anatomical Record|language=en|volume=296|issue=2|pages=257–272|doi=10.1002/ar.22637|pmid=23233318|s2cid=25260840|issn=1932-8494|doi-access=free}}</ref>

====Electroreception====
At least one species, the [[tucuxi]] or Guiana dolphin, is able to use [[electroreception]] to sense prey.<ref name=":0">{{cite web |last=Morell |first=Virginia |title=Guiana Dolphins Can Use Electric Signals to Locate Prey |work=Science |publisher=American Association for the Advancement of Science (AAAS) |date=July 2011 |url=http://news.sciencemag.org/sciencenow/2011/07/guiana-dolphins-can-use-electric.html?ref=hp |url-status=dead |archive-url=https://web.archive.org/web/20130530040210/http://news.sciencemag.org/sciencenow/2011/07/guiana-dolphins-can-use-electric.html?ref=hp |archive-date=2013-05-30 }}</ref>

=== Ears ===
Cetaceans are known to possess excellent hearing.<ref>{{cite web |last1=Mead |first1=James |title=Cetacea |url=https://school.eb.com/levels/high/article/cetacean/105982 |website=Britannica School High |publisher=Encyclopædia Britannica, Inc. |access-date=3 June 2019}}</ref>
[[File:Delfinekko.gif|thumb|upright=1.2|[[Biosonar]] ]]

The external ear has lost the [[Pinna (anatomy)|pinna]] (visible ear), but still retains a narrow [[ear canal]]. The three small bones or [[ossicles]] that transmit sound within each ear are [[Pachyosteosclerosis|dense and compact]], and differently shaped from those of land mammals. The semicircular canals are much smaller relative to body size than in other mammals.<ref name="Thewissen-Hearing">{{cite book | last=[[Hans Thewissen|Thewissen]] | first=J. G. M. | chapter=Hearing | pages=[https://archive.org/details/encyclopediaofma2002unse/page/570 570–572] | title=Encyclopedia of Marine Mammals | editor1-last=Perrin | editor1-first=William R. | editor2-last=Wiirsig | editor2-first=Bernd | editor3-last=[[Hans Thewissen|Thewissen]] | editor3-first=J. G. M. | year=2002 | publisher=Academic Press | isbn=978-0-12-551340-1 | chapter-url=https://archive.org/details/encyclopediaofma2002unse/page/570 }}</ref>

A bony structure of the middle and inner ear, the [[auditory bulla]], is composed of two compact and dense bones (the periotic and tympanic). It is housed in a cavity in the middle ear; in the Odontoceti (apart from in the [[Physeteroidea|physeterids]], this cavity is filled with dense foam{{clarify|what is the foam made of?|date=February 2025}} and completely surrounds the bulla, which is connected to the skull only by ligaments. This may isolate the ear from sounds transmitted through the bones of the skull, something that also happens in [[bat]]s.<ref>{{cite book | last=Ketten | first=Darlene R. | chapter=The Marine Mammal Ear: Specializations for Aquatic Audition and Echolocation | pages=717–750 | title=The Evolutionary Biology of Hearing | editor1-last=Webster | editor1-first=Douglas B. | editor2-last=Fay | editor2-first=Richard R. | editor3-last=Popper | editor3-first=Arthur N. | year=1992 | publisher=Springer | chapter-url=https://www.researchgate.net/publication/230691464}} Pages 725–727 used here.</ref>

Cetaceans use sound to [[communication|communicate]], using groans, moans, whistles, clicks or the 'singing' of the humpback whale.<ref name=":0" />

=== Echolocation ===
[[Odontoceti]] are generally capable of [[Animal echolocation|echolocation]].<ref name="emm">{{cite book |editor1-last=Perrin |editor1-first=William F. |editor2-last=Wursig |editor2-first=Bernd |editor3-last=[[Hans Thewissen|Thewissen]]|editor3-first=J. G. M. |title=Encyclopedia of Marine Mammals |last=Hooker |first=Sascha K. |edition=2 |publisher=Academic Press |page=1176 |year=2009 |isbn=978-0-12-373553-9 |url=https://books.google.com/books?id=2rkHQpToi9sC&q=Encyclopedia%20of%20Marine%20Mammals&pg=PP1}}</ref> They can discern the size, shape, surface characteristics, distance and movement of an object. They can search for, chase and catch fast-swimming prey in total darkness. Most Odontoceti can distinguish between prey and nonprey (such as humans or boats); captive Odontoceti can be trained to distinguish between, for example, balls of different sizes or shapes. Echolocation clicks also contain characteristic details unique to each animal, which may suggest that toothed whales can discern between their own click and that of others.<ref name="Obaldia2015Estimating">{{cite journal |author = de Obaldia, C., Simkus, G. & and Zölzer, U. | title = Estimating the number of sperm whale (Physeter macrocephalus) individuals based on grouping of corresponding clicks
 | journal = 41. Jahrestagung für Akustik (DAGA 2015), Nürnberg | year = 2015 | doi = 10.13140/RG.2.1.3764.9765 | url= https://www.researchgate.net/publication/277009691 }}</ref>

While differences in ear structure associated with echolocating abilities are found amongst Cetacea, cranial asymmetry has also been found to be a factor in the ability to produce sounds used in echolocation. Mysticeti, who don't have the ability to echolocate, possess general symmetry of the skull and facial region, while Odontoceti display a nasofacial asymmetry that is linked to their echolocating abilities.<ref name="auto">{{Cite journal |last1=Coombs |first1=Ellen J. |last2=Clavel |first2=Julien |last3=Park |first3=Travis |last4=Churchill |first4=Morgan |last5=Goswami |first5=Anjali |date=2020-07-10 |title=Wonky whales: the evolution of cranial asymmetry in cetaceans |journal=BMC Biology |volume=18 |issue=1 |pages=86 |doi=10.1186/s12915-020-00805-4 |doi-access=free |issn=1741-7007 |pmc=7350770 |pmid=32646447}}</ref> Differences in the level of asymmetry also seem to correlate with differences in the types of sounds produced.<ref name="auto"/>

Mysticeti have exceptionally thin, wide basilar membranes in their [[cochlea]]e without stiffening agents, making their ears adapted for processing low to [[infrasonic]] frequencies.<ref>{{cite journal | last = Ketten | first = Darlene R. | title = Structure and function in whale ears | year = 1997 | journal = The International Journal of Animal Sound and Its Recording | volume = 8 | issue = 1–2 | pages = 103–135 | url = http://csi.whoi.edu/sites/default/files/literature/Full%20Text_29.pdf | doi = 10.1080/09524622.1997.9753356 | bibcode = 1997Bioac...8..103K | access-date = 2013-12-21 | archive-date = 2014-08-01 | archive-url = https://web.archive.org/web/20140801161859/http://csi.whoi.edu/sites/default/files/literature/Full%20Text_29.pdf | url-status = dead }}</ref>

=== Chromosomes ===
The initial [[karyotype]] includes a set of [[chromosome]]s from 2n = 44. They have four pairs of telocentric chromosomes (whose [[centromeres]] sit at one of the [[telomeres]]), two to four pairs of subtelocentric and one or two large pairs of submetacentric chromosomes. The remaining chromosomes are metacentric—the centromere is approximately in the middle—and are rather small. All cetaceans have chromosomes 2n = 44, except the [[sperm whale]]s and [[pygmy sperm whale]]s, which have 2n = 42.<ref>{{cite journal|author=Ulfur Anarson|title=Comparative chromosome studies in Cetacea|journal=Institute of Genetics|year=1974|volume=77|issue=1|doi=10.1111/j.1601-5223.1974.tb01351.x|pages=1–36|pmid=4137586|doi-access=free}}</ref>