Gonochorism

 ( Reproduction ) 

In biology, gonochorism is a sexual system where there are two Sex and each individual organism is either male or female.

The term gonochorism is usually applied in animal species, the vast majority of which are gonochoric.

(2025). 9780128004265, Academic Press. . ISBN 9780128004265

Gonochorism contrasts with simultaneous hermaphroditism but it may be hard to tell if a species is gonochoric or sequentially hermaphroditic e.g. parrotfish, Patella ferruginea.

However, in gonochoric species individuals remain either male or female throughout their lives.

(2009). 9781400832019, Princeton University Press. . ISBN 9781400832019

Species that reproduce by Thelytokous and do not have males can still be classified as gonochoric.

(2019). 9781108499859, Cambridge University Press. . ISBN 9781108499859

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Terminology The term is derived from Greek language gone 'generation' + chorizein 'to separate'.

Philip Winn (2003). 9781134778157, Routledge. . ISBN 9781134778157

The term gonochorism originally came from German Gonochorismus.

Gonochorism is also referred to as unisexualism or gonochory.

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Evolution Gonochorism has evolved independently multiple times. It is very evolutionarily stable in animals. Its stability and advantages have received little attention.

(2019). 9783319941394, Springer. . ISBN 9783319941394

Gonochorism owes its origin to the evolution of anisogamy,

R. S. K. Barnes (1999). 9780865428348, John Wiley & Sons. . ISBN 9780865428348

but it is unclear if the evolution of anisogamy first led to hermaphroditism or gonochorism.

Gonochorism is thought to be the ancestral state in Polychaete, Hexacorallia,

Zvy Dubinsky (2010). 9789400701144, Springer Science & Business Media. . ISBN 9789400701144

Nematode,

Andreas Schmidt-Rhaesa (2013). 9783110274257, Walter de Gruyter. . ISBN 9783110274257

and hermaphroditic Fish. Gonochorism is thought to be ancestral in hermaphroditic fishes because it is widespread in basal of fish and other vertebrate lineages.

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

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Use across species

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Animals The term gonochorism is most often used for animal species, an estimated 95% of which are gonochoric. It is very common in vertebrate species, 99% of which are gonochoric.

(2018). 9780128151457, Academic Press. ISBN 9780128151457

Ninety-eight percent of fishes are gonochoric.

T. J. Pandian (2011). 9781439879191, CRC Press. . ISBN 9781439879191

(including

(2025). 9781429232524, Macmillan. . ISBN 9781429232524

(2010). 9780521879484, Cambridge University Press. . ISBN 9780521879484

) and are solely gonochoric.

(2018). 9784431566090, Springer. . ISBN 9784431566090

are almost always gonochoric.

James H. Thorp (2025). 9780123748553, Academic Press. . ISBN 9780123748553

Seventy-five percent of are gonochoric.

(2016). 9780128004265, Academic Press. . ISBN 9780128004265

Most including a majority of crustaceans are gonochoric.

Gonzalo Giribet (2020). 9780691197067, Princeton University Press. . ISBN 9780691197067

Thanumalaya Subramoniam (2016). 9780128096062, Academic Press. . ISBN 9780128096062

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

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Plants The term gonochorism is not usually applied to . which have single-sex individuals are called dioecy,

Henk Beentje (2025). 9781842466049, Royal Botanic Gardens, Kew. ISBN 9781842466049

while with single-sex individuals are dioicy. In , individual flowers may be hermaphroditic (i.e., with both stamens and ovaries) or dioecious (unisexual), having either no stamens (i.e., no male parts) or no ovaries (i.e., no female parts). Among flowering plants with unisexual flowers, some also produce hermaphrodite flowers, and the three types may occur in different arrangements on the same or separate plants. Plant species can thus be hermaphrodite, monoecious, Dioecy, Trioecy, polygamomonoecious, polygamodioecious, Andromonoecy, or gynomonoecious.

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

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Other reproductive strategies Gonochorism stands in contrast to other reproductive strategies such as asexual reproduction and hermaphrodite. Closely related taxa can have differing sexual strategies – for example, the genus Ophryotrocha contains species that are gonochoric and species that are hermaphrodites.

The sex of an individual may also change during its lifetimethis sequential hermaphroditism can, for example, be found in parrotfish and cockles.

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See also

• Diclinous
• Monoclinous
• Plant sexuality
• Gynogenesis

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