Editing Actinopterygii (section)

==Reproduction==
[[File:Gasterosteus aculeatus 1879.jpg|thumb|left|[[Three-spined stickleback]] (''Gasterosteus aculeatus'') males (red belly) build nests and compete to attract females to lay eggs in them. Males then defend and fan the eggs. Painting by [[Alexander Francis Lydon]], 1879]]
In nearly all ray-finned fish, the sexes are separate, and in most species the females spawn eggs that are fertilized externally, typically with the male inseminating the eggs after they are laid. Development then proceeds with a free-swimming larval stage.<ref>{{cite book |title=Zoology |url=https://archive.org/details/zoology0000dori |url-access=registration |last1=Dorit |first1=R.L. |last2=Walker |first2=W.F. |last3=Barnes |first3=R.D. |year=1991 |publisher=Saunders College Publishing |isbn=978-0-03-030504-7 |page=[https://archive.org/details/zoology0000dori/page/819 819] }}</ref> However other patterns of [[ontogeny]] exist, with one of the commonest being [[sequential hermaphroditism]]. In most cases this involves [[protogyny]], fish starting life as females and converting to males at some stage, triggered by some internal or external factor. [[Protandry]], where a fish converts from male to female, is much less common than protogyny.<ref>{{cite journal |title=Evolutionary perspectives on hermaphroditism in fishes |journal=Sexual Development |year=2009 |first=J.C. |last=Avise |author-link=John Avise |author2=Mank, J.E. |volume=3 |issue=2–3 |pages=152–163|doi=10.1159/000223079|pmid=19684459 |s2cid=22712745 |url=https://escholarship.org/uc/item/1px4b8qn }}</ref>

Most families use [[external fertilization|external]] rather than [[internal fertilization]].<ref name=Pitcher>{{cite book|last=Pitcher|first=T|title=The Behavior of Teleost Fishes|year=1993|publisher=Chapman & Hall|location=London}}</ref> Of the [[oviparity|oviparous]] teleosts, most (79%) do not provide parental care.<ref name=Reynolds>{{cite journal |last=Reynolds |first=John|author2=Nicholas B. Goodwin |author3=Robert P. Freckleton |title=Evolutionary Transitions in Parental Care and Live Bearing in Vertebrates |journal=Philosophical Transactions of the Royal Society B: Biological Sciences |date=19 March 2002 |volume=357 |issue=1419 |pmc=1692951 |pmid=11958696 |doi=10.1098/rstb.2001.0930 |pages=269–281}}</ref> [[Viviparity]], [[ovoviviparity]], or some form of parental care for eggs, whether by the male, the female, or both parents is seen in a significant fraction (21%) of the 422 teleost families; no care is likely the ancestral condition.<ref name=Reynolds /> The oldest case of viviparity in ray-finned fish is found in [[Middle Triassic]] species of {{extinct}}''[[Saurichthys]]''.<ref>{{cite journal | author = Maxwell | display-authors = etal | year = 2018 | title = Re-evaluation of the ontogeny and reproductive biology of the Triassic fish ''Saurichthys'' (Actinopterygii, Saurichthyidae) | journal = Palaeontology | volume = 61 | pages = 559–574 | doi = 10.5061/dryad.vc8h5 }}</ref> Viviparity is relatively rare and is found in about 6% of living teleost species; male care is far more common than female care.<ref name=Reynolds /><ref name=Clutton-Brock>{{cite book|last=Clutton-Brock|first=T. H.|author-link=Tim Clutton-Brock|title=The Evolution of Parental Care|year=1991|publisher=Princeton UP|location=Princeton, NJ}}</ref> Male territoriality [[exaptation|"preadapts"]] a species for evolving male parental care.<ref name=Werren>{{cite journal |last=Werren |first=John|author2=Mart R. Gross |author3=Richard Shine |author3-link=Richard Shine |title=Paternity and the evolution of male parentage |journal=Journal of Theoretical Biology |year=1980 |volume=82|issue=4 |doi=10.1016/0022-5193(80)90182-4 |pmid=7382520|url=https://www.researchgate.net/publication/222458526 |access-date=15 September 2013 |pages=619–631}}</ref><ref name=Baylis>{{cite journal |last=Baylis |first=Jeffrey |title=The Evolution of Parental Care in Fishes, with reference to Darwin's rule of male sexual selection |journal=Environmental Biology of Fishes |year=1981 |volume=6 |issue=2 |doi=10.1007/BF00002788 |pages=223–251|bibcode=1981EnvBF...6..223B |s2cid=19242013 }}</ref>

There are a few examples of fish that self-fertilise. The [[mangrove rivulus]] is an amphibious, simultaneous hermaphrodite, producing both eggs and spawn and having internal fertilisation. This mode of reproduction may be related to the fish's habit of spending long periods out of water in the mangrove forests it inhabits. Males are occasionally produced at temperatures below {{convert|19|°C}} and can fertilise eggs that are then spawned by the female. This maintains genetic variability in a species that is otherwise highly inbred.<ref name=Wootton>{{cite book|author1=Wootton, Robert J.|author2=Smith, Carl|title=Reproductive Biology of Teleost Fishes|url=https://books.google.com/books?id=_YnjBAAAQBAJ|year=2014|publisher=Wiley |isbn=978-1-118-89139-1}}</ref>

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