Editing Dolphin (section)

==Anatomy==

[[File:Dolphin Anatomy.svg|thumb|upright=1.35|The anatomy of a dolphin showing its skeleton, major organs, tail and body shape.]]
Dolphins have torpedo-shaped bodies with generally non-flexible necks, limbs modified into flippers, a tail fin, and bulbous heads. Dolphin skulls have small eye orbits, long snouts, and eyes placed on the sides of its head; they lack external ear flaps. Dolphins range in size from the {{cvt|1.7|m|ftin}} long and {{convert|50|kg|lb|abbr=on}} [[Maui's dolphin]] to the {{convert|9.5|m|ftin|abbr=on}} and {{convert|10|MT|ST|abbr=on}} [[orca]]. Overall, they tend to be dwarfed by other [[Cetartiodactyl]]s. Several species have female-biased sexual dimorphism, with the females being larger than the males.<ref>{{cite book |url=http://www.cetus.ucsd.edu/SIO133/PDF/Sexual%20Dimorphism.pdf |title=Sexual Dimorphism |author1=Katherine Ralls |author2=Sarah Mesnick |pages=1005–1011 |access-date=August 29, 2015 |archive-url=https://web.archive.org/web/20190725004132/http://www.cetus.ucsd.edu/SIO133/PDF/Sexual%20Dimorphism.pdf |archive-date=July 25, 2019 |url-status=dead }}</ref><ref name="Cetacean anatomy">{{cite web |url=http://acsonline.org/wp-content/uploads/2011/03/ACS-Cetacean-Curriculum.pdf |title=Cetacean Curriculum&nbsp;– A teacher's guide to introducing and using whales, dolphins, & porpoises in the classroom |date=November 28, 2004 |publisher=American Cetacean Society |access-date=December 20, 2013 |quote=Sound production in cetaceans is a complex phenomenon not fully understood by scientists. |archive-url=https://web.archive.org/web/20120807092419/http://acsonline.org/wp-content/uploads/2011/03/ACS-Cetacean-Curriculum.pdf |archive-date=August 7, 2012 |url-status=dead |df=mdy-all }}</ref>

Dolphins have conical teeth, as opposed to [[porpoise]]s' spade-shaped teeth. These conical teeth are used to catch swift prey such as fish, squid or large mammals, such as seals.<ref name="Cetacean anatomy"/>

Breathing involves expelling stale air from their [[blowhole (anatomy)|blowhole]], in an upward blast, which may be visible in cold air, followed by inhaling fresh air into the lungs. Dolphins have rather small, unidentifiable spouts.<ref name="Cetacean anatomy"/><ref>{{cite journal |last=Scholander |first=Per Fredrik |title=Experimental investigations on the respiratory function in diving mammals and birds |year=1940 | journal=Hvalraadets Skrifter | volume=22 }}</ref>

All dolphins have a thick layer of [[blubber]], thickness varying on climate. This blubber can help with buoyancy, protection to some extent as predators would have a hard time getting through a thick layer of fat, and energy for leaner times; the primary usage for blubber is insulation from the harsh climate. Calves, generally, are born with a thin layer of blubber, which develops at different paces depending on the habitat.<ref name="Cetacean anatomy"/><ref name="Dolphins"/>

Dolphins have a two-chambered<ref name=Stevens1995>{{cite book |author1=Stevens, C. Edward |author2=Hume, Ian D. |title=Comparative Physiology of the Vertebrate Digestive System |publisher=Cambridge University Press |page=317 |year=1995}}</ref> or three-chambered<ref name=Biancani2022>{{cite journal |last1= Biancani |first1= B. |last2= Galosi |first2= L. |display-authors=etal |date= October 2022 |title= Comparative study of the gastric mucosa of Risso's dolphin (''Grampus griseus'') and bottlenose dolphin (''Tursiops truncatus'') |journal= Veterinary Sciences |volume= 9 |issue= 10 |pages= 571 |doi= 10.3390/vetsci9100571|doi-access= free |pmid= 36288184 |pmc= 9609225 |hdl= 11581/485468 |hdl-access= free }}</ref> stomach that is similar in cellular structure to that of terrestrial carnivores. They have [[Fundic stomach|fundic]] and [[Pyloric stomach|pyloric]] chambers.<ref name=Stevens1995/>

Dolphins' reproductive organs are located inside the body, with genital slits on the ventral (belly) side. Males have two slits, one concealing the [[penis]] and one further behind for the [[anus]].<ref name="PerrinWursig2009">{{cite book|author1=William F. Perrin|author2=Bernd Wursig|author3=J. G.M. [[Hans Thewissen|Thewissen]]|title=Encyclopedia of Marine Mammals|url={{google books|plainurl=y|id=2rkHQpToi9sC}}|access-date=June 28, 2013|date=February 26, 2009|publisher=Academic Press|isbn=978-0-08-091993-5}}</ref> Females have one genital slit, housing the [[vagina]] and the anus, with a [[Mammary gland|mammary slit]] on either side.<ref>{{cite book|author=Carol J. Howard |title=Dolphin Chronicles |url={{google books|plainurl=y|id=pewZhNQ7jggC|page=129}} |access-date=November 26, 2012 |date=December 1, 1995 |publisher=Random House Digital, Inc. |isbn=978-0-553-37778-1 |pages=129–}}</ref><ref>{{cite book|author1=Bernd G. Würsig |author2=Bernd Wursig, Melany Wursig |title=The Dusky Dolphin: Master Acrobat Off Different Shores |url={{google books|plainurl=y|id=KudBOfRXjWAC|page=156}} |access-date=November 26, 2012 |year=2010 |publisher=Academic Press |isbn=978-0-12-373723-6 |pages=156–}}</ref><ref>{{cite book|author1=Edward F. Gibbons Jr. |author2=Barbara Susan Durrant |author3=Jack Demarest |title=Conservation Endangered Spe: An Interdisciplinary Approach |url={{google books|plainurl=y|id=OuYcepU_YjMC|page=435}} |access-date=November 26, 2012 |year=1995 |publisher=SUNY Press |isbn=978-0-7914-1911-3 |pages=435–}}</ref>

=== Integumentary system ===
The integumentary system is an organ system mostly consisting of skin, hair, nails and endocrine glands. The skin of dolphins is specialized to satisfy specific requirements, including protection, fat storage, heat regulation, and sensory perception. The skin of a dolphin is made up of two parts: the epidermis and the blubber, which consists of two layers including the dermis and subcutis.<ref name="Cozzi-2017">{{Cite book|last1=Cozzi|first1=Bruno|title=Anatomy of Dolphins: Insights into Body Structure and Function|last2=Huggenberger|first2=Stefan|last3=Oelschläger|first3=Helmut|publisher=Elsevier Inc.|year=2017|isbn=978-0124072299|pages=23}}</ref>

The dolphin's skin is known to have a smooth rubber texture and is without hair and glands, except mammary glands. At birth, a newborn dolphin has hairs lined up in a single band on both sides of the rostrum, which is their jaw, and usually has a total length of 16–17&nbsp;cm .<ref name="Cozzi-2017" /> The epidermis is characterized by the lack of keratin and by a prominent intertwine of epidermal [[rete pegs]] and long dermal papillae.<ref name="Cozzi-2017" /> The epidermal rete pegs are the epithelial extensions that project into the underlying connective tissue in both skin and mucous membranes. The dermal papillae are finger-like projections that help adhesion between the epidermal and dermal layers, as well as providing a larger surface area to nourish the epidermal layer.<ref>{{Cite web|last1=Paxton|first1=Steve|last2=Peckham|first2=Michelle|last3=Knibbs|first3=Adele|date=2003|title=The Leeds Histology Guide|url=https://www.histology.leeds.ac.uk/skin/skin_layers.php|language=en}}</ref> The thickness of a dolphin's epidermis varies, depending on species and age.

==== Blubber ====
Blubber is found within the dermis and subcutis layer. The dermis blends gradually with the adipose layer, which is known as fat, because the fat may extend up to the epidermis border and collagen fiber bundles extend throughout the whole subcutaneous blubber which is fat found under the skin.<ref name="Cozzi-2017" /> The thickness of the subcutaneous blubber or fat depends on the dolphin's health, development, location, reproductive state, and how well it feeds. This fat is thickest on the dolphin's back and belly. Most of the dolphin's body fat is accumulated in a thick layer of blubber. Blubber differs from fat in that, in addition to fat cells, it contains a fibrous network of connective tissue.<ref>{{Cite web|title=All About Bottlenose Dolphins – Adaptations|url=https://seaworld.org/animals/all-about/bottlenose-dolphin/adaptations/|access-date=2020-12-06|website=seaworld.org}}</ref>

The blubber functions to streamline the body and to form specialized locomotor structures such as the dorsal fin, propulsive fluke blades and caudal keels.<ref name="Cozzi-2017" /> There are many nerve endings that resemble small, onion-like configurations that are present in the superficial portion of the dermis. Mechanoreceptors are found within the interlocks of the epidermis with dermal ridges. There are nerve fibers in the dermis that extend to the epidermis. These nerve endings are known to be highly [[proprioception|proprioceptive]], which explains sensory perception.<ref name="Cozzi-2017" /> Proprioception, which is also known as kinesthesia, is the body's ability to sense its location, movements and actions. Dolphins are sensitive to vibrations and small pressure changes.<ref name="Kremers">{{cite journal|display-authors=3 | last1=Kremers | first1=Dorothee | last2=Célérier | first2=Aurélie | last3=Schaal | first3=Benoist | last4=Campagna | first4=Sylvie | last5=Trabalon | first5=Marie | last6=Böye | first6=Martin | last7=Hausberger | first7=Martine | last8=Lemasson | first8=Alban | title=Sensory Perception in Cetaceans: Part I—Current Knowledge about Dolphin Senses As a Representative Species | journal=Frontiers in Ecology and Evolution | volume=4 | date=2016-05-11 | issn=2296-701X | doi=10.3389/fevo.2016.00049 | page= 49| doi-access=free | bibcode=2016FrEEv...4...49K }}</ref> Blood vessels and nerve endings can be found within the dermis. There is a plexus of parallel running arteries and veins in the dorsal fin, fluke, and flippers.<ref name="Cozzi-2017" /> The blubber manipulates the blood vessels to help the dolphin stay warm. When the temperature drops, the blubber constricts the blood vessels to reduce blood flow in the dolphin.<ref>{{Cite web|title=How Does Blubber Keep Animals Warm?|url=https://animals.mom.com/blubber-keep-animals-warm-2735.html|access-date=2020-12-06|website=animals.mom.com|language=en|archive-date=January 25, 2021|archive-url=https://web.archive.org/web/20210125141647/https://animals.mom.com/blubber-keep-animals-warm-2735.html|url-status=dead}}</ref> This allows the dolphin to spend less energy heating its own body, ultimately keeping the animal warmer without burning energy as quick. In order to release heat, the heat must pass the blubber layer. There are thermal windows that lack blubber, are not fully insulated and are somewhat thin and highly vascularized, including the dorsal fin, flukes, and flippers.<ref name="WDC-2012">{{Cite web|date=2012-10-27|title=How does blubber keep whales warm?|url=https://us.whales.org/2012/10/27/how-does-blubber-keep-whales-warm/|access-date=2020-12-06|website=Whale & Dolphin Conservation USA|language=en-US}}</ref> These thermal windows are a good way for dolphins to get rid of excess heat if overheating. Additionally in order to conserve heat, dolphins use countercurrent heat exchange. Blood flows in different directions in order for heat to transfer across membranes. Heat from warm blood leaving the heart will heat up the cold blood that is headed back to the heart from the extremities, meaning that the heart always has warm blood and it decreases the heat lost to the water in those thermal windows.<ref name="WDC-2012" />

===Locomotion===
Dolphins have two pectoral flippers, each containing four digits, a boneless [[dorsal fin]] for stability, and a fluke for propulsion. Although dolphins do not possess external hind limbs, some possess discrete rudimentary appendages, which may contain feet and digits. Orcas are fast swimmers in comparison to seals which typically cruise at {{convert|9|–|28|km/h|mph|abbr=on}}; the orca, in comparison, can travel at speeds up to {{convert|55.5|km/h|mph|abbr=on}}.{{Citation needed|date=February 2024}} A study of a Pacific white-sided dolphin in an aquarium found fast burst acceleration, with the individual being able with 5 strokes (2.5 fluke beats) to go from 5.0 m s-1 to 8.7 m s-1 in 0.7 seconds.<ref name="Tanaka Li Uchida Nakamura 2019 p. e0210860">{{cite journal |last1=Tanaka |first1=Hiroto |last2=Li |first2=Gen |last3=Uchida |first3=Yusuke |last4=Nakamura |first4=Masashi |last5=Ikeda |first5=Teruaki |last6=Liu |first6=Hao |date=2019 |title=Measurement of time-varying kinematics of a dolphin in burst accelerating swimming |journal=PLOS ONE |volume=14 |issue=1 |page=e0210860 |doi=10.1371/journal.pone.0210860 |issn=1932-6203 |pmc=6353170 |pmid=30699184 |doi-access=free|bibcode=2019PLoSO..1410860T }}</ref>

The fusing of the neck vertebrae, while increasing stability when swimming at high speeds, decreases flexibility, which means most dolphins are unable to turn their heads.<ref>{{cite web|url=http://yellowmagpie.com/beluga-whale/ |title=Beluga Whale: The White Melon-headed Creature Of The Cold |publisher=Yellowmagpie.com |date=June 27, 2012 |access-date=August 12, 2013}}</ref><ref>{{cite web |url=http://www.whalesalive.org.au/aboutwhales.html |title=About Whales |publisher=Whalesalive.org.au |date=June 26, 2009 |access-date=August 12, 2013 |archive-url=https://web.archive.org/web/20130812000655/http://whalesalive.org.au/aboutwhales.html |archive-date=August 12, 2013 |url-status=dead }}</ref> [[River dolphin]]s have non-fused neck vertebrae and can turn their heads up to 90°.<ref>{{cite journal|url=http://acsonline.org/fact-sheets/boto-amazon-river-dolphin/|title=Boto (Amazon river dolphin) ''Inia geoffrensis''|journal=American Cetacean Society|year=2002|access-date=September 12, 2015}}</ref> Dolphins swim by moving their fluke and rear body vertically, while their flippers are mainly used for steering. Some species [[Cetacean surfacing behaviour#Porpoising|porpoise]] out of the water, which allows them to travel faster. Their skeletal anatomy allows them to be fast swimmers. All species have a [[dorsal fin]] to prevent themselves from involuntarily spinning in the water.<ref name="Cetacean anatomy" /><ref name="Dolphins">{{cite book |author1=Klinowska, Margaret |author2=Cooke, Justin |year=1991 |title=Dolphins, Porpoises, and Whales of the World: the IUCN Red Data Book |url=https://portals.iucn.org/library/sites/library/files/documents/RD-1991-001.pdf |access-date=August 29, 2015}}</ref>

Some dolphins are adapted for diving to great depths. In addition to their streamlined bodies, some can selectively slow their [[heart rate]] to conserve oxygen.<ref name="phys-dolphins">{{cite news |title=Dolphins conserve oxygen and prevent dive-related problems by consciously decreasing their heart rates before diving |url=https://phys.org/news/2020-11-dolphins-oxygen-dive-related-problems-consciously.html |access-date=8 December 2020 |work=phys.org |language=en}}</ref><ref>{{cite journal |last1=Fahlman |first1=Andreas |last2=Cozzi |first2=Bruno |last3=Manley |first3=Mercy |last4=Jabas |first4=Sandra |last5=Malik |first5=Marek |last6=Blawas |first6=Ashley |last7=Janik |first7=Vincent M. |title=Conditioned Variation in Heart Rate During Static Breath-Holds in the Bottlenose Dolphin (Tursiops truncatus) |journal=[[Frontiers in Physiology]] |date=2020 |volume=11 |page=604018 |doi=10.3389/fphys.2020.604018 |pmid=33329056 |pmc=7732665 |s2cid=227128277 |language=en |issn=1664-042X|doi-access=free }} [[File:CC-BY icon.svg|50px]] Available under [https://creativecommons.org/licenses/by/4.0/ CC BY 4.0].</ref> Some can also re-route blood from tissue tolerant of water pressure to the heart, brain and other organs. Their [[hemoglobin]] and [[myoglobin]] store oxygen in body tissues, and they have twice as much myoglobin as hemoglobin.<ref>{{cite journal |author1=Norena, S. R. |author2=Williams, T. M. |title=Body size and skeletal muscle myoglobin of cetaceans: adaptations for maximizing dive duration |journal= Comparative Biochemistry and Physiology. Part A, Molecular & Integrative Physiology|volume=126 |issue=2 |year=2000 |pages=181–191|doi=10.1016/s1095-6433(00)00182-3 |pmid=10936758}}</ref>

===Senses===
[[File:Delfinekko.gif|thumb|[[Biosonar]] by cetaceans]]
[[File:Toothed whale sound production.svg|upright=1.35|Diagram illustrating sound generation, propagation, and reception in a toothed whale. Outgoing sounds are in cyan and incoming ones are in green]]

A dolphin ear has specific adaptations to the [[Marine (ocean)|marine]] environment. In humans, the [[middle ear]] works as an impedance equalizer between the outside air's low [[Acoustic impedance|impedance]] and the [[cochlea]]r fluid's high impedance. In dolphins, and other marine mammals, there is no great difference between the outer and inner environments. Instead of sound passing through the outer ear to the middle ear, dolphins receive sound through the throat, from which it passes through a low-impedance fat-filled cavity to the inner ear. The ear is acoustically isolated from the skull by air-filled sinus pockets, which allow for greater directional hearing underwater.<ref>{{cite journal |author=Nummela, Sirpa |title=Sound transmission in archaic and modern whales: Anatomical adaptations for underwater hearing |journal=The Anatomical Record |volume=290 |issue=6 |pages=716–733 |year=2007 |doi=10.1002/ar.20528 |last2=Thewissen|first2=J.G.M |last3=Bajpai |first3=Sunil |last4=Hussain |first4=Taseer |last5=Kumar |first5=Kishor |pmid=17516434|s2cid=12140889 |url=http://repository.ias.ac.in/4651/1/321.pdf |author2-link=Hans Thewissen |doi-access=free }}<!--|access-date=August 29, 2015 --></ref> 

Dolphins generate sounds independently of respiration using recycled air that passes through air sacs and phonic (alternatively monkey) lips. Integral to the lips are oil-filled organs called dorsal bursae that have been suggested to be homologous to the sperm whale's spermaceti organ.<ref name="n010">{{cite journal |last1=Cranford |first1=Ted W. |last2=Amundin |first2=Mats |last3=Norris |first3=Kenneth S. |date=1996 |title=Functional morphology and homology in the odontocete nasal complex: Implications for sound generation |journal=Journal of Morphology |volume=228 |issue=3 |pages=223–285 |doi=10.1002/(SICI)1097-4687(199606)228:3<223::AID-JMOR1>3.0.CO;2-3 |pmid=8622183 |issn=0362-2525}}</ref> High-frequency clicks pass through the sound-modifying organs of the extramandibular fat body, intramandibular fat body and the [[melon (cetacean)|melon]]. This melon consists of fat, and the skull of any such creature containing a melon will have a large depression. This allows dolphins to use [[Animal echolocation|echolocation]] for orientation.<ref name="Cetacean anatomy" /><ref name="Dolphin senses">{{cite book |editor1=Thomas, Jeanette A. |editor2=Kastelein, Ronald A. |title=Sensory Abilities of Cetaceans: Laboratory and Field Evidence |volume=196 |isbn=978-1-4899-0860-5 |doi=10.1007/978-4899-0858-2 |year=2002 |url={{google books |plainurl=y |id=VWz1BwAAQBAJ}}|doi-broken-date=November 1, 2024 }}</ref><ref name="Thewissen-Hearing">{{cite book|editor-first1=William F. |editor-last1=Perrin|editor-first2=Bernd |editor-last2= Wursig|editor-first3=J.G.M. 'Hans' |editor-last3=[[Hans Thewissen|Thewissen]]|title=Encyclopedia of Marine Mammals|url={{google books |plainurl=y |id=2rkHQpToi9sC}}|date=February 26, 2009|publisher=Academic Press|isbn=978-0-08-091993-5}}</ref><ref>{{cite book |last=Ketten |first=Darlene R.|chapter=The Marine Mammal Ear: Specializations for Aquatic Audition and Echolocation |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 |access-date=March 1, 2013 |pages=725–727}}</ref><ref>{{Cite book
|title=A Proposed Echolocation Receptor for the Bottlenose Dolphin (''Tursiops truncatus''): Modelling the Receive Directivity from Tooth and Lower Jaw Geometry ''NATO ASI Series A: Sensory Abilities of Cetaceans'' |volume=196|pages=255–267
|location=NY
|publisher=Plenum
|year=1990
|isbn=978-0-306-43695-6
|editor1=Jeanette A. Thomas |editor2=Ronald A. Kastelein. }}</ref> Though most dolphins do not have hair, they do have [[hair follicle]]s that may perform some sensory function.<ref>{{cite journal
|title= Selective heating of vibrissal follicles in seals (''Phoca vitulina'') and dolphins (''Sotalia fluviatilis guianensis'')
|author1=Bjorn Mauck |author2=Ulf Eysel |author3=Guide Dehnhardt |journal=Journal of Experimental Biology |year=2000
|volume=203 |issue=14 |pages=2125–2131 |doi=10.1242/jeb.203.14.2125 |pmid=10862725 |bibcode=2000JExpB.203.2125M |url=http://jeb.biologists.org/cgi/reprint/203/14/2125.pdf
|access-date= March 11, 2007}}</ref> Beyond locating an object, [[Animal echolocation|echolocation]] also provides the animal with an idea on an object's shape and size, though how exactly this works is not yet understood.<ref>{{cite journal|last=Harley|first=Heidi E.|author2=DeLong, Caroline M.|title=Echoic Object Recognition by the Bottlenose Dolphin|journal=Comparative Cognition & Behavior Reviews|year=2008|volume=3|pages=45–65|doi=10.3819/ccbr.2008.30003|doi-access=free}}</ref> The small hairs on the rostrum of the [[boto]] (river dolphins of South America) are believed to function as a [[somatosensory system|tactile sense]], possibly to compensate for the boto's poor eyesight.<ref>{{cite web|title= Amazon River Dolphin (''Inia geoffrensis'')|first=Laurie|last=Stepanek|date=May 19, 1998|publisher=Texas Marine Mammal Stranding Network|url=http://www.tmmsn.org/mmgulf/inia_geoffrensis.html|access-date= November 20, 2013 |archive-url = https://web.archive.org/web/20070206051622/http://www.tmmsn.org/mmgulf/inia_geoffrensis.html |archive-date = February 6, 2007}}</ref>

A dolphin eye is relatively small for its size, yet they do retain a good degree of eyesight. As well as this, the eyes of a dolphin are placed on the sides of its head, so their vision consists of two fields, rather than a binocular view like humans have. When dolphins surface, their lens and cornea correct the nearsightedness that results from the water's refraction of light. Their eyes contain both [[rod cell|rod]] and [[cone cell|cone]] cells, meaning they can see in both dim and bright light, but they have far more rod cells than they do cone cells. They lack short wavelength sensitive visual pigments in their cone cells, indicating a more limited capacity for color vision than most mammals.<ref>{{cite journal |author1=Mass, Alla M. |author2=Supin, Alexander Y. A.  |title=Adaptive features of aquatic mammals' eyes |journal=Anatomical Record |volume=290 |issue=6 |pages=701–715 |date=May 21, 2007 |doi=10.1002/ar.20529 |pmid=17516421|s2cid=39925190 |doi-access=free }}</ref> Most dolphins have slightly flattened eyeballs, enlarged pupils (which shrink as they surface to prevent damage), slightly flattened corneas and a ''[[tapetum lucidum]]'' (eye tissue behind the retina); these adaptations allow for large amounts of light to pass through the eye and, therefore, a very clear image of the surrounding area. They also have glands on the eyelids and [[corneal epithelium|outer corneal layer]] that act as protection for the cornea.<ref name="Dolphin senses"/>

The [[olfactory lobes]] and [[olfactory nerve|nerve]] are absent in dolphins, suggesting that they have no sense of smell.<ref name="Dolphin senses"/>

Dolphins are not thought to have a good sense of taste, as their taste buds are atrophied or missing altogether. Some have preferences for different kinds of fish, indicating some ability to taste.<ref name="Dolphin senses"/>