Editing Pygmy sperm whale (section)

==Anatomy==
[[File:Zwergpottwal Kogia breviceps DSC 0071.jpg|thumb|Closeup of the head]]
Like its giant relative, the [[sperm whale]], the pygmy sperm whale has a [[spermaceti]] organ in its forehead (see [[sperm whale]] for a discussion of its purpose). It also has a sac in its intestines that contains a dark red fluid. The whale may expel this fluid when frightened, perhaps to confuse and disorient predators.<ref name=Scott1987>{{cite journal |author1=Scott, M.D.  |author2=Cordaro, J.G.  |name-list-style=amp | year = 1987 | title = Behavioral observations of the dwarf sperm whale, ''Kogia simus'' | journal = Marine Mammal Science | volume = 3 | issue = 4 | pages = 353–354 | doi = 10.1111/j.1748-7692.1987.tb00322.x|bibcode=1987MMamS...3..353S }}</ref>

Dwarf and pygmy sperm whales possess the shortest rostrum of current day cetaceans with a skull that is greatly asymmetrical.<ref>Mcalpine, Donald F. "Pygmy and dwarf sperm whales: Kogia breviceps and K. sima." ''Encyclopedia of Marine Mammals (Second Edition)''. 2009. 936-938.</ref>

Pygmy sperm whales have from 50 to 55 [[vertebra]]e, and from 12 to 14 [[rib]]s on either side, although the latter are not necessarily symmetrical, and the hindmost ribs do not connect with the vertebral column. Each of the flippers has seven [[Carpal bones|carpals]], and a variable number of [[phalanges]] in the digits, reportedly ranging from two in the [[thumb|first digit]] to as many as 10 in the second digit. No true [[hip bone|innominate bone]] exists; it is replaced by a sheet of dense [[connective tissue]]. The [[hyoid bone]] is unusually large, and presumably has a role in the whale's suction feeding.<ref name="Bloodworth2008" />
[[File:Pygmy sperm whale skull.jpg|thumb|Pygmy sperm whale skull viewed from the side.]]

===Teeth===
The pygmy sperm has between 20 and 32 teeth, all of which are set into the [[Anatomical terms of location#Cranial and caudal|rostral]] part of the lower jaw.<ref name=Bloodworthetal2008>{{cite journal | author = Bloodworth Brian E., Odell Daniel K. | year = 2008 | title = Kogia breviceps | url = http://www.deepdyve.com/lp/allen-press/kogia-breviceps-cetacea-kogiidae-wM6JPlBunF/10 | journal = Mammalian Species | volume = 819 | pages = 1–12 | doi=10.1644/819.1| doi-access = free }}</ref> Unusually, adults lack [[Tooth enamel|enamel]] due to a mutation in [[MMP20|the enamelysin gene]],<ref>{{Cite journal | doi=10.1098/rspb.2010.1280| pmid=20861053| pmc=3049022| title=Pseudogenization of the tooth gene enamelysin (MMP20) in the common ancestor of extant baleen whales| journal=Proceedings of the Royal Society B: Biological Sciences| volume=278| issue=1708| pages=993–1002| year=2010| last1=Meredith| first1=R. W.| last2=Gatesy| first2=J.| last3=Cheng| first3=J.| last4=Springer| first4=M. S.}}</ref> although enamel is present in very young individuals.<ref name=Bloodworth2008>{{cite journal |author1=Bloodworth, B.E.  |author2=Odell, D.K.  |name-list-style=amp | year = 2008 | title = ''Kogia breviceps'' (Cetacea: Kogiidae) | journal = Mammalian Species | pages = Number 819: pp. 1–12 | doi = 10.1644/819.1 | volume=819| doi-access = free }}</ref>

[[File:Pygmy_sperm_whale_teeth.jpg|thumb|200px|Pygmy whale teeth on its lower rostrum]]

===Melon===
[[file:Kogia breviceps sagittal + coronal.svg|left|thumb|300px]]Like other [[toothed whale]]s, the pygmy sperm whale has a "[[melon (whale)|melon]]", a body of fat and wax in the head that it uses to focus and modulate the sounds it makes.<ref name=Clarke2003>{{cite journal | author = Clarke, M.R. | year = 2003 | title = Production and control of sound by the small sperm whale, ''Kogia breviceps'' and ''K. sima'' and their implications for other Cetacea | journal = Journal of the Marine Biological Association of the United Kingdom | volume = 83 | issue = 2 | pages = 241–263 | doi = 10.1017/S0025315403007045h| bibcode = 2003JMBUK..83..241C | s2cid = 84103043 }}</ref> The inner core of the melon has a higher wax content than the outer cortex. The inner core transmits sound more slowly than the outer layer, allowing it to refract sound into a highly directional beam.<ref name=Karoletal978>R., Karol; C., Litchfield; D., Caldwell; M., Caldwell (1978). ''Compositional topography of melon and spermaceti organ lipids in the pygmy sperm whale Kogia breviceps: Implications for echolocation''. Marine Biology, Volume 47 (2)</ref> Behind the melon, separated by a thin membrane, is the [[spermaceti organ]]. Both the melon and the spermaceti organ are encased in a thick fibrous coat, resembling a [[Synovial bursa|bursa]].<ref name=Cranford1996>{{cite journal | author = Cranford, T.W.| year = 1996 | title = Functional morphology and homology in the odontocete nasal complex: implications for sound generation | journal = Journal of Morphology | volume = 228 | issue = 2 | pages = 223–285 | doi = 10.1002/(SICI)1097-4687(199606)228:3<223::AID-JMOR1>3.0.CO;2-3 | pmid=8622183| s2cid = 35653583 |display-authors=etal}}</ref> The whale produces sound by moving air through the right nasal cavity, which includes a valvular structure, or ''museau de singe'', with a thickened vocal reed, functioning like the [[vocal cord]]s of humans.

===Stomach===
The stomach has three chambers. The first chamber, or forestomach, is not glandular, and opens directly into the second, fundic chamber, which is lined by digestive glands. A narrow tube runs from the second to the third, or pyloric, stomach, which is also glandular, and connects, via a [[sphincter]], to the [[duodenum]]. Although fermentation of food material apparently occurs in the [[small intestine]], no [[caecum]] is present.<ref name=Hagey1993>{{cite journal | author = Hagey, L.R.| year = 1993 | title = Biliary bile acid composition of the Physeteridae (sperm whales) | journal = Marine Mammal Science | volume = 9 | issue = 1 | pages = 23–33 | doi = 10.1111/j.1748-7692.1993.tb00423.x| bibcode = 1993MMamS...9...23H |display-authors=etal}}</ref>

===Brain===
The rostroventral dura of the brain contains a significant concentration of magnetite crystals, which suggests that ''K. breviceps'' can navigate by [[magnetoreception]].<ref name=Bloodworth2008/>

Studies have also shown that compared to the [[sperm whale]], the pygmy sperm whale brain has significantly fewer neurons, which may be connected to a decreased complexity in social interaction and group-based living.<ref>{{cite journal |last1=Poth, Fung, Gunturkun, Ridgway |title=Neuron numbers in sensory corticies of five delphinids compared to a physterid, the pygmy perm whale |journal=Brain Research Bulletin |date=2005-02-25 |volume=66 |issue=357–360|pages=357–360 |doi=10.1016/j.brainresbull.2005.02.001 |pmid=16144614 |s2cid=14822113 }}</ref>

===Microbiome===
Samples of blowhole mucus from a rescued pygmy sperm whale were studied between 1993 and 1994, during its rehabilitation. These samples included blood cells and a variety of microbes, such as various [[ciliate]]s, [[yeast]]-like organisms and [[bacteria]], although these were seen intermitently. One new species of microorganism, the [[flagellate]] ''[[Jarrellia atramenti]]'', was decribed from these samples, and was consistently observed throughout the period of rehabilitation. This flagellate is considered a normal, benign microbial component of the respiratory tract of this whale species.<ref name="Poynton-2001">{{cite journal|last=Poynton|first=S. L.|last2=Whitaker|first2=B. R.|last3=Heinrich|first3=A. B.|title=A novel trypanoplasm-like flagellate ''Jarrellia atramenti'' n. g., n. sp. (Kinetoplastida: Bodonidae) and ciliates from the blowhole of a stranded pygmy sperm whale ''Kogia breviceps'' (Physeteridae): morphology, life cycle and potential pathogenicity|journal=Diseases of Aquatic Organisms|volume=44|date=10 April 2001|issn=0177-5103|doi=10.3354/dao044191|pages=191–201|url=https://www.int-res.com/articles/dao/44/d044p191.pdf|archive-url=https://web.archive.org/web/20180724090019/https://www.int-res.com/articles/dao/44/d044p191.pdf|archive-date=24 July 2018}}</ref><ref name="Stamper-2006">{{cite journal|last=Stamper|first=M. Andrew|last2=Whitaker|first2=Brent R.|last3=Schofield|first3=T. David|title=Case study: morbidity in a pygmy sperm whale ''Kogia breviceps'' due to ocean-bourne plastic|journal=Marine Mammal Science|volume=22|issue=3|date=4 May 2006|issn=0824-0469|doi=10.1111/j.1748-7692.2006.00062.x|pages=719–722}}</ref>