Hermaphrodite

Source: Wikipedia, the free encyclopedia.
For other uses, see Hermaphrodite (disambiguation).
Not to be confused with Intersex people or Intersex (biology).
Garden snails mating

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

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

gynomonoecy
).

Hermaphrodism is not to be confused with intersexuality, which is a separate and unrelated phenomenon. While intersex people are commonly referred to as hermaphrodites in medical literature, this usage is now considered to be stigmatizing and misleading,[7][8] as intersex people do not have functional sets of both male and female organs.[9][10] People previously incorrectly categorized as "true" hermaphrodites are now called with having Ovotesticular Syndrome.

Etymology

The term hermaphrodite derives from the

English lexicon as early as the late fourteenth century.[14]

Animals

Sequential hermaphrodites

Main article: Sequential hermaphroditism
Shells of Crepidula fornicata (common slipper shell)
Clownfish are initially male; the largest fish in a group becomes a female.
Most species of parrotfish start life as females and later change into males.

Sequential hermaphrodites (

Michael T. Ghiselin[18]
which states that if an individual of a certain sex could significantly increase its reproductive success after reaching a certain size, it would be to their advantage to switch to that sex.

Sequential hermaphrodites can be divided into three broad categories:

Dichogamy can have both conservation-related implications for humans, as mentioned above, as well as economic implications. For instance,

aquacultured. Since the adults take several years to change from female to male, the broodstock
are extremely valuable individuals.

Simultaneous hermaphrodites

Turbellarians mating by penis fencing. Each has two penises on the undersides of their heads which they use to inject sperm.
Earthworms are simultaneous hermaphrodites, having both male and female reproductive organs.

Self-fertilization often occurs.[citation needed
]

  • Pulmonate land snails and land slugs are perhaps the best-known kinds of simultaneous hermaphrodites, and are the most widespread of terrestrial animals possessing this sexual polymorphism. Sexual material is exchanged between both animals via spermatophores, and is then stored in the spermatheca. After exchange of spermatozoa, both animals will lay fertilized eggs after a period of gestation. The eggs will proceed to hatch after a development period. Snails typically reproduce from early spring through late autumn.[21]
  • Banana slugs are an example of a hermaphroditic gastropod. Mating with a partner is more desirable biologically than self-fertilization, as the genetic material of the resultant offspring is varied, but if mating with a partner is not possible, self-fertilization is practiced. The male sexual organ of an adult banana slug is quite large in proportion to its size, as well as compared to the female organ. It is possible for banana slugs, while mating, to become stuck together. If a substantial amount of wiggling fails to separate them, the male organ will be bitten off (using the slug's radula), see apophallation. If a banana slug has lost its male sexual organ, it can still mate as a female, making hermaphroditism a valuable adaptation.[22]
  • The species of colourful
    sea slugs Goniobranchus reticulatus is hermaphroditic, with both male and female organs active at the same time during copulation. After mating, the external portion of the penis detaches, but is able to regrow within 24 hours.[23][24]
  • Earthworms are another example of a simultaneous hermaphrodite. Although they possess ovaries and testes, they have a protective mechanism against self-fertilization. Sexual reproduction occurs when two worms meet and exchange gametes, copulating on damp nights during warm seasons.
  • The free-living hermaphroditic nematode Caenorhabditis elegans reproduces primarily by self-fertilization, but infrequent out-crossing events occur at a rate of approximately 1%.[25]
  • Hamlets do not practice self-fertilization, but a pair will mate multiple times over several nights, taking turns between which one acts as the male and which acts as the female.[26][failed verification
    ]
  • The mangrove killifish (Kryptolebias marmoratus) are simultaneous hermaphrodites, producing both eggs and sperm and routinely reproducing by self-fertilization. Each individual normally fertilizes itself when an egg and sperm produced by an internal organ unite inside the fish's body.[27] This species is also regarded as the only known vertebrate species that can reproduce by self fertilization.[28]

Pseudohermaphroditism

Main article: Pseudohermaphroditism

When spotted hyenas were first scientifically observed by explorers, they were thought to be hermaphrodites. Early observations of spotted hyenas in the wild led researchers to believe that all spotted hyenas, male and female, were born with what appeared to be a penis. The apparent penis in female spotted hyenas is in fact an enlarged clitoris, which contains an external birth canal.[29][30] It can be difficult to determine the sex of wild spotted hyenas until sexual maturity, when they may become pregnant. When a female spotted hyena gives birth, they pass the cub through the cervix internally, but then pass it out through the elongated clitoris.[31]

Plants

Main articles:
Sexual reproduction in plants and Plant reproductive morphology § Bisexual
carpels and stamens
.

The term hermaphrodite is used in

carpellate (female, ovule-producing) parts. The overwhelming majority of flowering plant species are hermaphroditic.[32]

Monoecy

Flowering plant species with separate, imperfect, male and female flowers on the same individual are called

conifers are almost all monoecious.[35] Some plants can change their sex throughout their lifetime, a phenomenon called sequential hermaphroditism.[citation needed
]

Andromonecy

In andromonecious species, the plants produce perfect (hermaphrodite) flowers and separate fertile male flowers that are sterile as female.[36][37] Andromonecy occurs in about 4000 species of flowering plants (2% of flowering plants).[38]

Gynomonoecy

In gynomonoecious species, the plants produce hermaphrodite flowers and separate male-sterile pistillate flowers.[36] One example is the meadow saxifrage, Saxifraga granulata.[39] Charles Darwin gave several other examples in his 1877 book "The Different Forms of Flowers on Plants of the Same Species".[40]

About 57% of moss species and 68% of liverworts are unisexual, meaning that their gametophytes produce either male or female gametes, but not both.[41]: 377 

Sequential hermaphroditism is common in bryophytes and some vascular plants.[citation needed]

Use regarding humans

Intersex topics
Intersex flag
Human rights and legal issues
Medicine and biology
Society and culture
History and events
Rights by country
See also
Main article: Intersex
Hermaphroditus, the "son" of the Greek god Hermes and the goddess Aphrodite, origin of the word "hermaphrodite"
The Obando Fertility Rites in the Philippines, before becoming a Catholic festival, was initially an Anitist ritual dedicated to the hermaphrodite deity, Lakapati, who presided over fertility.[42]
Nadar of an intersex person displaying genitalia, one of a nine-part series. The series may be the earliest medical photographic documentation of an intersex person.[43]

Historically, the term hermaphrodite was used in law to refer to people whose sex was in doubt. The 12th-century Decretum Gratiani states that "Whether an hermaphrodite may witness a testament, depends on which sex prevails" ("Hermafroditus an ad testamentum adhiberi possit, qualitas sexus incalescentis ostendit.").[44][45].

Alexander ab Alexandro (1461–1523) stated, using the term hermaphrodite, that the people who bore the sexes of both man and woman were regarded by the Athenians and the Romans as monsters, and thrown into the sea at Athens and into the Tiber at Rome.[46]
Similarly, the 17th-century English jurist and judge Edward Coke (Lord Coke), wrote in his Institutes of the Lawes of England on laws of succession stating, "Every heire is either a male, a female, or an hermaphrodite, that is both male and female. And an hermaphrodite (which is also called Androgynus) shall be heire, either as male or female, according to that kind of sexe which doth prevaile."[47][48]

During the

true hermaphrodites if their gonadal tissue contained both testicular and ovarian tissue, or pseudohermaphrodites if their external appearance (phenotype) differed from sex expected from internal gonads. This language has fallen out of favor due to misconceptions and stigma associated with the terms,[50][51][8][10]
and also a shift to nomenclature based on genetics.

The term intersex describes a wide variety of combinations of what are considered male and female biological characteristics. Intersex biology may include, for example, ambiguous-looking external genitalia, karyotypes that include mixed XX and XY chromosome pairs (46XX/46XY, 46XX/47XXY or 45X/XY mosaic). Clinically, medicine currently describes intersex people as having disorders of sex development,[52] a term that has been vigorously challenged.[53] This is particularly significant because of the relationship between medical terminology and medical intervention.[54]

medical interventions
designed to make intersex bodies more typically male or female.

In some cases, intersex traits are caused by unusual levels of sex hormones, which may be the result of an atypical set of sex chromosomes.[

testicular and ovarian tissues will both be present in the same individual.[57]

Fetuses before sexual differentiation are sometimes described as female by doctors explaining the process.[58][page needed] This is not technically true. Before this stage, humans are simply undifferentiated and possess a paramesonephric duct, a mesonephric duct, and a genital tubercle.[citation needed]

Evolution

Main article: Evolution of sexual reproduction
For evolution of mixed sexual systems, see Trioecy § Evolution of trioecy, Androdioecy § Evolution of androdioecy, and Gynodioecy § Evolution.

The evolution of anisogamy may have contributed to the evolution of simultaneous hermaphroditism and sequential hermaphroditism,[6] but it remains unclear if the evolution of anisogamy first led to hermaphroditism or gonochorism.[59]: 213  It is possible that hermaphroditism evolved from gonochorism, or vice versa. Most studies on its evolution focus on plants, and its evolution in animals is unclear as of December 2017.[60]

Simultaneous hermaphroditism that exclusively reproduces through self-fertilization has evolved many times in plants and animals, but it might not last long evolutionarily.[61]: 14 

In animals

paraphyletic Spiralia, assignments of sexual modes for the phylum level than the species level, and methods exclusively based on maximum parsimony.[60]

Hermaphroditism is

polyphyletic in invertebrates where it evolved from gonochorism[1]: 97  and gonochorism is also ancestral to hermaphroditic fishes.[62] According to Nelson Çabej simultaneous hermaphroditism in animals most likely evolved due to a limited number of mating partners.[63]

In plants

See also: Monoecy § Evolution, Andromonoecy § Evolution, and Gynomonoecy § Evolution

It is widely accepted that the first vascular plants were outcrossing hermaphrodites.[64] In flowering plants, hermaphroditism is ancestral to dioecy.[65]

Hermaphroditism in plants may promote self fertilization in pioneer populations.[66] However, plants have evolved multiple different mechanisms to avoid self-fertilization in hermaphrodites, including sequential hermaphroditism, molecular recognition systems and mechanical or morphological mechanisms such as heterostyly.[67]: 73, 74 

See also

References

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Further reading

External links

Look up hermaphrodite in Wiktionary, the free dictionary.
Wikimedia Commons has media related to Hermaphrodites.
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