Editing Testicle (section)

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The basal condition for mammals is to have internal testes.<ref name="Kleisner">{{cite journal |last1= Kleisner |first1= Karel |last2= Ivell |first2= Richard |last3= Flegr |first3= Jaroslav |date= March 2010|title= The evolutionary history of testicular externalization and the origin of the scrotum |url=http://www.ias.ac.in/article/fulltext/jbsc/035/01/0027-0037  |journal= Journal of Biosciences |publisher= Indian Academy of Sciences |volume= 35 |issue= 1 |pages= 27–37 |doi=  10.1007/s12038-010-0005-7 |pmid= 20413907 |s2cid= 11962872 |access-date=8 December 2018 |archive-url=https://web.archive.org/web/20180225094002/http://www.ias.ac.in/article/fulltext/jbsc/035/01/0027-0037 |archive-date=25 February 2018 |url-status=dead }}</ref> The testes of [[monotremes]],<ref name="Griffiths2012">{{cite book|author=Mervyn Griffiths|title=The Biology of the Monotremes|url=https://books.google.com/books?id=W7nu16_DkTgC&q=testes+OR+scrotum|date=2 December 2012|publisher=Elsevier Science|isbn=978-0-323-15331-7|access-date=19 October 2020|archive-date=29 June 2023|archive-url=https://web.archive.org/web/20230629161534/https://books.google.com/books?id=W7nu16_DkTgC&q=testes+OR+scrotum|url-status=live}}</ref><ref name="NowakWalker1999">{{cite book|author1=Ronald M. Nowak|author2=Ernest Pillsbury Walker|title=Walker's Mammals of the World|url=https://archive.org/details/walkersmammalsof0001nowa|url-access=registration|quote=testes.|date=29 July 1999|publisher=JHU Press|isbn=978-0-8018-5789-8}}</ref> [[xenarthra]]ns,<ref name="NowakWalker1999"/> and [[afrotheria]]ns<ref name="FowlerMikota2008">{{cite book|author1=Murray Fowler|author2=Susan K. Mikota|title=Biology, Medicine, and Surgery of Elephants|url=https://books.google.com/books?id=A3GFYySwY1cC&q=testes+OR+testis+OR+testicles|date=9 January 2008|publisher=John Wiley & Sons|isbn=978-0-470-34411-8|access-date=19 October 2020|archive-date=29 June 2023|archive-url=https://web.archive.org/web/20230629161516/https://books.google.com/books?id=A3GFYySwY1cC&q=testes+OR+testis+OR+testicles|url-status=live}}</ref> remain within the abdomen ([[testicondy]]). There are also some [[marsupial]]s with external testes<ref name="Hunsaker2012">{{cite book|author=Don II Hunsaker|title=The Biology of Marsupials|url=https://books.google.com/books?id=cESCLrRJGm0C&q=testes+OR+testis+OR+testicles|date=2 December 2012|publisher=Elsevier Science|isbn=978-0-323-14620-3|access-date=19 October 2020|archive-date=29 June 2023|archive-url=https://web.archive.org/web/20230629161542/https://books.google.com/books?id=cESCLrRJGm0C&q=testes+OR+testis+OR+testicles|url-status=live}}</ref><ref name="Tyndale-Biscoe2005">{{cite book|author=C. Hugh Tyndale-Biscoe|title=Life of Marsupials|url=https://books.google.com/books?id=KqtlPZJ9y8EC&q=testes+OR+testis+OR+testicles|year=2005|publisher=Csiro Publishing|isbn=978-0-643-06257-3|access-date=2020-10-19|archive-date=2023-06-29|archive-url=https://web.archive.org/web/20230629161517/https://books.google.com/books?id=KqtlPZJ9y8EC&q=testes+OR+testis+OR+testicles|url-status=live}}</ref><ref name="Tyndale-BiscoeRenfree1987">{{cite book|author1=Hugh Tyndale-Biscoe|author2=Marilyn Renfree|title=Reproductive Physiology of Marsupials|url=https://books.google.com/books?id=HpjovN0vXW4C&q=testes|date=30 January 1987|publisher=Cambridge University Press|isbn=978-0-521-33792-2|access-date=19 October 2020|archive-date=29 June 2023|archive-url=https://web.archive.org/web/20230629161518/https://books.google.com/books?id=HpjovN0vXW4C&q=testes|url-status=live}}</ref> and [[boreoeutheria]]n mammals with internal testes, such as the rhinoceros.<ref name="rhinoresourcecenter.com">Schaffer, N. E., et al. "[http://www.rhinoresourcecenter.com/pdf_files/125/1258623199.pdf Ultrasonography of the reproductive anatomy in the Sumatran rhinoceros (Dicerorhinus sumatrensis)] {{Webarchive|url=https://web.archive.org/web/20170923194033/http://www.rhinoresourcecenter.com/pdf_files/125/1258623199.pdf |date=2017-09-23 }}." Journal of Zoo and Wildlife Medicine (1994): 337-348.</ref> [[Cetaceans]] such as whales and dolphins also have internal testes.<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> As external testes would increase drag in the water, they have internal testes, which are kept cool by special circulatory systems that cool the arterial blood going to the testes by placing the arteries near veins bringing cooled venous blood from the skin.<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> In [[odobenid]]s and [[phocid]]s, the location of the testes is para-abdominal, though [[otariid]]s have scrotal testes.<ref name="GullandDierauf2018">{{cite book|author1=Frances M.D. Gulland|author2=Leslie A. Dierauf|author3=Karyl L. Whitman|title=CRC Handbook of Marine Mammal Medicine|url=https://books.google.com/books?id=b1ZSDwAAQBAJ|date=20 March 2018|publisher=CRC Press|isbn=978-1-351-38416-2|access-date=23 January 2020|archive-date=29 June 2023|archive-url=https://web.archive.org/web/20230629161820/https://books.google.com/books?id=b1ZSDwAAQBAJ|url-status=live}}</ref>