Hermaphrodite

A hermaphrodite (/hərˈmæfrəˌdaɪt/) is a sexually reproducing organism that produces both male and female gametes.^[1] Animal species in which individuals are of different sexes, either male or female but not both, are gonochoric, which is the opposite of hermaphroditic.^[2]

The individuals of many taxonomic groups of animals, primarily invertebrates, are hermaphrodites, capable of producing viable gametes of both sexes. In the great majority of tunicates, mollusks, and earthworms, hermaphroditism is a normal condition, enabling a form of sexual reproduction in which either partner can act as the female or male. Hermaphroditism is also found in some fish species, but is rare in other vertebrate groups. Most hermaphroditic species exhibit some degree of self-fertilization. The distribution of self-fertilization rates among animals is similar to that of plants, suggesting that similar pressures are operating to direct the evolution of selfing in animals and plants.^[3]

A rough estimate of the number of hermaphroditic animal species is 65,000, about 5% of all animal species, or 33% excluding insects. Insects are almost exclusively gonochoric, and no definitive cases of hermaphroditism have been demonstrated in this group.^[4] There are no known hermaphroditic species among mammals^[5] or birds.^[6]

About 94% of flowering plant species are either hermaphroditic (all flowers produce both male and female gametes) or monoecious, where both male and female flowers occur on the same plant. There are also mixed breeding systems, in both plants and animals, where hermaphrodite individuals coexist with males (called androdioecy) or with females (called gynodioecy), or all three exist in the same species (called trioecy). Sometimes, both male and hermaphrodite flowers occur on the same plant (andromonoecy) or both female and hermaphrodite flowers occur on the same plant (gynomonoecy).

Hermaphrodism is not to be confused with ovotesticular syndrome in mammals, which is a separate and unrelated phenomenon. While people with the condition were previously called "true hermaphrodites" in medical literature, this usage is now considered to be outdated as of 2006 and misleading,^[7]^[8] as people with ovotesticular syndrome do not have functional sets of both male and female organs.^[9]^[10]

^ Avise JC (2011-03-18). Hermaphroditism: A Primer on the Biology, Ecology, and Evolution of Dual Sexuality. Columbia University Press. pp. 1–7. ISBN 978-0-231-52715-6.
^ Holub AM, Shackelford TK (2020). "Gonochorism". In Vonk J, Shackelford TK (eds.). Encyclopedia of Animal Cognition and Behavior (PDF). Cham: Springer International Publishing. pp. 1–3. doi:10.1007/978-3-319-47829-6_305-1. ISBN 978-3-319-47829-6. S2CID 240938739.
^ Jarne P, Auld JR (September 2006). "Animals mix it up too: the distribution of self-fertilization among hermaphroditic animals". Evolution; International Journal of Organic Evolution. 60 (9): 1816–24. doi:10.1554/06-246.1. PMID 17089966. S2CID 23849389.
^ Royer, M (1975). "Hermaphroditism in Insects. Studies on Icerya purchasi". In Reinboth, R (ed.). Intersexuality in the Animal Kingdom. Berlin, Heidelberg: Springer. pp. 135–145. doi:10.1007/978-3-642-66069-6_14. ISBN 978-3-642-66071-9.
^ Gorshkov V (2012-12-06). Physical and Biological Bases of Life Stability: Man, Biota, Environment. Springer Science & Business Media. ISBN 978-3-642-85001-1.
^ Schärer L (February 2017). "The varied ways of being male and female". Molecular Reproduction and Development. 84 (2): 94–104. doi:10.1002/mrd.22775. PMID 28032683. Of note, the otherwise well-studied insects, birds, and mammals are strikingly absent here—with not a single species among these groups showing hermaphroditism (for details on a supposedly hermaphroditic scale insect, however, see Gardner and Ross, 2011).
^ Herndon A. "Getting Rid of "Hermaphroditism" Once and For All". Intersex Society of North America. Archived from the original on 27 September 2011. Retrieved 2 October 2011.
^ "Is a person who is intersex a hermaphrodite?". Intersex Society of North America. Retrieved 2024-01-20. The mythological term "hermaphrodite" implies that a person is both fully male and fully female. This is a physiologic impossibility. The words "hermaphrodite" and "pseudo-hermaphrodite" are stigmatizing and misleading words.
^ Rosenfield KA (2018), "Hermaphrodite", in Vonk J, Shackelford T (eds.), Encyclopedia of Animal Cognition and Behavior, Cham: Springer International Publishing, pp. 1–2, doi:10.1007/978-3-319-47829-6_329-1, ISBN 978-3-319-47829-6
^ Mills A (2018-01-01). Biology of Sex. University of Toronto Press. p. 309. ISBN 978-1-4875-9337-7. In the past, the term hermaphrodite was widely applied in such cases, but humans are not hermaphroditic. In a truly hermaphroditic species, individuals have functional sets of male and female organs.

[Avise-1] Avise JC (2011-03-18). Hermaphroditism: A Primer on the Biology, Ecology, and Evolution of Dual Sexuality. Columbia University Press. pp. 1–7. ISBN 978-0-231-52715-6.

[Holub-2] Holub AM, Shackelford TK (2020). "Gonochorism". In Vonk J, Shackelford TK (eds.). Encyclopedia of Animal Cognition and Behavior (PDF). Cham: Springer International Publishing. pp. 1–3. doi:10.1007/978-3-319-47829-6_305-1. ISBN 978-3-319-47829-6. S2CID 240938739.

[Jarne-3] Jarne P, Auld JR (September 2006). "Animals mix it up too: the distribution of self-fertilization among hermaphroditic animals". Evolution; International Journal of Organic Evolution. 60 (9): 1816–24. doi:10.1554/06-246.1. PMID 17089966. S2CID 23849389.

[Royer-4] Royer, M (1975). "Hermaphroditism in Insects. Studies on Icerya purchasi". In Reinboth, R (ed.). Intersexuality in the Animal Kingdom. Berlin, Heidelberg: Springer. pp. 135–145. doi:10.1007/978-3-642-66069-6_14. ISBN 978-3-642-66071-9.

[Gorshkov-5] Gorshkov V (2012-12-06). Physical and Biological Bases of Life Stability: Man, Biota, Environment. Springer Science & Business Media. ISBN 978-3-642-85001-1.

[Schärer-6] Schärer L (February 2017). "The varied ways of being male and female". Molecular Reproduction and Development. 84 (2): 94–104. doi:10.1002/mrd.22775. PMID 28032683. Of note, the otherwise well-studied insects, birds, and mammals are strikingly absent here—with not a single species among these groups showing hermaphroditism (for details on a supposedly hermaphroditic scale insect, however, see Gardner and Ross, 2011).

[Herndon-7] Herndon A. "Getting Rid of "Hermaphroditism" Once and For All". Intersex Society of North America. Archived from the original on 27 September 2011. Retrieved 2 October 2011.

[:0-8] "Is a person who is intersex a hermaphrodite?". Intersex Society of North America. Retrieved 2024-01-20. The mythological term "hermaphrodite" implies that a person is both fully male and fully female. This is a physiologic impossibility. The words "hermaphrodite" and "pseudo-hermaphrodite" are stigmatizing and misleading words.

[Rosenfield-9] Rosenfield KA (2018), "Hermaphrodite", in Vonk J, Shackelford T (eds.), Encyclopedia of Animal Cognition and Behavior, Cham: Springer International Publishing, pp. 1–2, doi:10.1007/978-3-319-47829-6_329-1, ISBN 978-3-319-47829-6

[Mills-10] Mills A (2018-01-01). Biology of Sex. University of Toronto Press. p. 309. ISBN 978-1-4875-9337-7. In the past, the term hermaphrodite was widely applied in such cases, but humans are not hermaphroditic. In a truly hermaphroditic species, individuals have functional sets of male and female organs.

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