Biology:Intersex

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Short description: Sex characteristics between male and female


Intersex is a general term for an organism that has sex characteristics that are between male and female.[1] It typically applies to a minority of members of gonochoric animal species such as mammals (as opposed to hermaphroditic species in which the majority of members can have both male and female sex characteristics).[2] Such organisms are usually sterile.[3]

Intersexuality can occur due to both genetic and environmental factors[4] and has been reported in mammals, fishes, nematodes, and crustaceans.

Mammals

Intersex can also occur in mammals such as humans and pigs, with it being estimated that 0.1% to 1.4% of pigs are intersex.[5] In Vanuatu, Narave pigs are sacred intersex pigs that are found on Malo Island. An analysis of Navare pig mitochondrial DNA by Lum et al. (2006) found that they are descended from Southeast Asian pigs.[6][7][8]

At least six different mole species have an intersex adaption where by the female mole has an ovotestis, "a hybrid organ made up of both ovarian and testicular tissue. This effectively makes them intersex, giving them an extra dose of testosterone to make them just as muscular and aggressive as male moles". The ovarian part of the ovotestis is reproductively functional.[9][10]

Intersexuality in humans is relatively rare. Depending on the definition, the prevalence of intersex among humans have been reported to range from 0.018%[11][12] to up to 1.7% of humans.[13]

Nematodes

Intersex is known to occur in all main groups of nematodes. Most of them are functionally female. Male intersexes with female characteristics have been reported but are less common.[14]

Fishes

Gonadal intersex also occurs in fishes, where the individual has both ovarian and testicular tissue. Although it is a rare anomaly among gonochoric fishes, it is a transitional state in fishes that are protandric or protogynous.[15] Intersexuality has been reported in 23 fish families.[16]

Crustaceans

The oldest evidence for intersexuality in crustaceans comes from fossils dating back 70 million years ago.[4] Intersex has been reported in gonochoric crustaceans as early as 1729. A large amount of literature exists on intersexuality for isopoda and amphipoda, with there being reports of both intersex males and intersex females.[17]

See also

References

  1. ↑ "intersex | Definition & Facts" (in en). https://www.britannica.com/science/intersex. "Intersex, in biology, an organism having physical characteristics intermediate between a true male and a true female of its species." 
  2. ↑ (in en) Encyclopedia of Fish Physiology: From Genome to Environment. Academic Press. 2011-06-01. ISBN 978-0-08-092323-9. https://books.google.com/books?id=3bsgS125KH0C&q=gonochoric+intersex+encyclopedia&pg=PP3932. "Thus, strictly speaking, all hermaphrodites are intersex at one time point, but not all intersexes are hermaphrodites. This definition is usually applied to gonochoristic species to describe those individuals that are not normal for the species." 
  3. ↑ "Malformation - Sexual anomalies" (in en). Encyclopædia Britannica, Inc.. https://www.britannica.com/science/malformation/Sexual-anomalies. 
  4. ↑ 4.0 4.1 Ford, Alex T. (February 2012). "Intersexuality in Crustacea: an environmental issue?". Aquatic Toxicology (Amsterdam, Netherlands) 108: 125–129. doi:10.1016/j.aquatox.2011.08.016. ISSN 1879-1514. PMID 22265612. https://pubmed.ncbi.nlm.nih.gov/22265612/. 
  5. ↑ Hunter, R. H. F.; Hunter, Ronald Henry Fraser (1995-03-09) (in en). Sex Determination, Differentiation and Intersexuality in Placental Mammals. Cambridge University Press. pp. 157. ISBN 978-0-521-46218-1. https://books.google.com/books?id=OKo6cjqjYs4C&dq=intersex+mammals&pg=PA157. 
  6. ↑ Lum, J. Koji; McIntyre, James K.; Greger, Douglas L.; Huffman, Kirk W.; Vilar, Miguel G. (November 14, 2006). "Recent Southeast Asian domestication and Lapita dispersal of sacred male pseudohermaphroditic "tuskers" and hairless pigs of Vanuatu". Proceedings of the National Academy of Sciences 103 (46): 17190–17195. doi:10.1073/pnas.0608220103. PMID 17088556. 
  7. ↑ "Intersex Pigs". Southwest Pacific Research Project. http://www.swprp.org/intersexual-pigs. 
  8. ↑ "Pigs in Paradise". Penn State University. https://www.psu.edu/news/research/story/pigs-paradise/. 
  9. ↑ https://www.cbc.ca/radio/quirks/oct-17-coronavirus-and-pain-sampling-an-asteroid-intersex-moles-and-more-1.5763905/female-moles-are-intersex-they-have-testicle-like-tissue-that-helps-them-grow-big-and-tough-1.5763925,CBC Radio, accessed 2023-04-13
  10. ↑ M. Real, Francisca; Haas, Stefan A.; Franchini, Paolo; Xiong, Peiwen; Simakov, Oleg; Kuhl, Heiner; Schöpflin, Robert; Heller, David et al. (2020). "The mole genome reveals regulatory rearrangements associated with adaptive intersexuality" (in en). Science 370 (6513): 208–214. doi:10.1126/science.aaz2582. PMID 33033216. 
  11. ↑  , Wikidata Q34163911
  12. ↑ Selma Feldman Witchel (2018). "Disorders of Sex Development". Best Practice & Research. Clinical Obstetrics & Gynaecology 48: 90–102. doi:10.1016/j.bpobgyn.2017.11.005. ISSN 1521-6934. PMID 29503125. ""The estimated frequency of genital ambiguity is reported to be in the range of 1:2000-1:4500"". 
  13. ↑ "Intersex people | OHCHR". United Nations. October 24, 2019. https://www.ohchr.org/en/sexual-orientation-and-gender-identity/intersex-people. 
  14. ↑ El-Bawab, Fatma (2020-01-18) (in en). Invertebrate Embryology and Reproduction. Academic Press. pp. 431. ISBN 978-0-12-814115-1. https://books.google.com/books?id=m_rKDwAAQBAJ&dq=gonochorism+invertebrates&pg=PA293. 
  15. ↑ Norris, David O.; Lopez, Kristin H. (2010-11-25) (in en). Hormones and Reproduction of Vertebrates. Academic Press. pp. 249–251. ISBN 978-0-08-095809-5. https://books.google.com/books?id=HKv3mC5Eb34C&dq=intersex+fishes&pg=PA250. 
  16. ↑ Pandian, T. J. (2010-09-15) (in en). Sexuality in Fishes. CRC Press. pp. 38. ISBN 978-1-4398-4669-8. https://books.google.com/books?id=nUP7CAAAQBAJ&q=intersexuality+in+fishes. 
  17. ↑ Cothran, Rickey; Thiel, Martin (2020-04-24) (in en). The Natural History of the Crustacea: Reproductive Biology: Volume VI. Oxford University Press. pp. 395–396. ISBN 978-0-19-068855-4. https://books.google.com/books?id=847UDwAAQBAJ. 




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