Gonochorism

Source: Wikipedia, the free encyclopedia.
Not to be confused with sexual dimorphism.

In biology, gonochorism is a sexual system where there are two sexes and each individual organism is either male or female.[1] The term gonochorism is usually applied in animal species, the vast majority of which are gonochoric.[2]: 212–222 

Gonochorism contrasts with

thelytokous parthenogenesis and do not have males can still be classified as gonochoric.[5][clarification needed
]

Terminology

Look up gonochorism, gonochory, or unisexualism in Wiktionary, the free dictionary.

The term is derived from Greek (gone, generation) + (chorizein, to separate).[6] The term gonochorism originally came from German Gonochorismus.[7]

Gonochorism is also referred to as unisexualism or gonochory.

Evolution

Main article: Evolution of sexual reproduction
For evolution of dioecy in plants, see Dioecy § Evolution of dioecy.

Gonochorism has evolved independently multiple times.[8] It is very evolutionarily stable in animals.[9] Its stability and advantages have received little attention.[10]: 46  Gonochorism owes its origin to the evolution of anisogamy,[11] but it is unclear if the evolution of anisogamy first led to hermaphroditism or gonochorism.[2]: 213 

Gonochorism is thought to be ancestral in polychaetes,[9]: 126  hexacorallia,[12]: 74  nematodes,[13]: 62  and hermaphroditic fishes. Gonochorism is thought to be ancestral in hermaphroditic fishes because it is widespread in basal clades of fish and other vertebrate lineages.[14]

Two papers from 2008 have suggested that transitions between hermaphroditism and gonochorism or vice versa have occurred in animals between 10 and 20 times.[15] In a 2017 study involving 165 taxon groups, more evolutionary transitions from gonochorism to hermaphroditism were found than the reverse.[16]

Use across species

Animals

The term is most often used with animals, in which the species are usually gonochoric.

Gonochorism has been estimated to occur in 95% of animal species.[17] It is very common in vertebrate species, 99% of which are gonochoric.[18][19] 98% of fishes are gonochoric.[20] Mammals (including humans[21][22]) and birds are solely gonochoric.[23]

Tardigrades are almost always gonochoric.[24] 75% of snails are gonochoric.[25]

Most arthropods are gonochoric.[26] For example a majority of crustaceans are gonochoric.[27]

In animals, sex is most often genetically determined, but may be determined by other mechanisms. For example, alligators use temperature-dependent sex determination during egg incubation.

Plants

gynomonoecious
.

flatworms, schistosomes
are gonochoric. The narrow female can be seen emerging from the thicker male's gynecophoral canal below his ventral sucker.

Examples of species with gonochoric or dioecious pollination include hollies and kiwifruit. In these plants the male plant that supplies the pollen is referred to as the pollenizer.

Other reproductive strategies

Gonochorism stands in contrast to other

reproductive strategies such as asexual reproduction and hermaphroditism. Closely related taxa can have differing sexual strategies – for example, the genus Ophryotrocha contains species that are gonochoric and species that are hermaphrodites.[30]

The sex of an individual may also change during its lifetime – this sequential hermaphroditism can, for example, be found in parrotfish[31][32] and cockles.

See also

  • Diclinous
  • Monoclinous
  • Plant sexuality

References

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  7. ^ "Definition of GONOCHORISM". www.merriam-webster.com. Archived from the original on 2021-09-29. Retrieved 2021-09-29.
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  31. ^ Bester C. "Stoplight parrotfish". Florida Museum of Natural History, Ichthyology Department. Archived from the original on 6 December 2009. Retrieved 15 December 2009.
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