Livebearers: Difference between revisions
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{{Short description|Fish that give birth to free swimming offspring}} |
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'''Live-bearing aquarium fish''' are [[fish]] of certain species which are ''[[ovo-viviparous]]''. This means that while the fry still incubate inside eggs, these eggs are not expelled at an early stage of their development, but are retained within the female's body and the fry are allowed to hatch inside her before they are expelled. These fish, for example the [[Poecilia reticulata|guppy]], are among the most popular [[List of freshwater aquarium fish species|aquarium fish]]. |
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[[Image:Poecilia reticulata Fry DSC04357 nevit.jpg|thumb|[[Guppy]] fry]] |
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'''Livebearers''' are [[fish]] that retain their eggs inside the body and give birth to live, free-swimming young. They are especially prized by aquarium owners. Among aquarium fish, livebearers are nearly all members of the family [[Poeciliidae]] and include: [[guppies]], [[Sailfin molly|mollies]], [[platies]] and [[swordtail]]s.<ref name="Alderton2012">{{cite book|url=https://books.google.com/books?id=BKIKBgAAQBAJ|title=Livebearers: Understanding Guppies, Mollies, Swordtails and Others|author=David Alderton|date=15 May 2012|publisher=CompanionHouse Books|isbn=978-1-62008-006-1}}</ref> |
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The advantages of livebearing to the aquarist are that the newborn [[juvenile fish]] are larger than newly-hatched fry, have a lower chance of mortality and are easier to care for. Unusual livebearers include [[seahorse]]s and [[pipefish]], where the males care for the young, and certain [[cichlid]]s that are [[mouthbrooder]]s, with the parent incubating the eggs in the [[mouth|buccal cavity]]. |
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[[Placentalia|Placental mammals]], on the other hand, are ''viviparous'', and have dropped the egg stage altogether. |
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==Common aquarium livebearers== |
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Almost all popular live-bearing aquarium fish belong to the family [[Poecilidae]], that is, the [[Poecilia reticulata|guppies]], [[Poecilia latipinna|mollies]], [[Xiphoporus maculatus|platies]] and [[Xiphoporus helleri|swordtails]], but half beaks and some species of [[shark]]s and [[ray (fish)|ray]]s also bear live young. |
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<!-- These aren't common and should not be listed under common! And not all sharks and rays are livebearers. The [[coelacanth]], [[Embiotocidae| surf perches]], and many types of [[shark| sharks]] and [[Batoidea|rays]] are all livebearing fish, aquarists do not usually keep these.-->Species of interest to aquarists are almost always members of the family [[Poeciliidae]], most commonly [[Guppy|guppies]], [[Sailfin molly|mollies]], [[Platy (fish)|platies]], [[Xiphophorus|swordtails]], [[Poecilia wingei|Endler's livebearer]], and [[mosquitofish]]. Most of these are [[ovoviviparous]], with the developing embryos receiving no nourishment from the parent fish, but a few are [[viviparous]], receiving food from the maternal blood supply. {{Cn|date=April 2021}} |
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Because the newborn fish are large compared to the fry of [[oviparity|oviparous]] fish, <!-- Added clarification to oviparous.-->which are those that lay eggs, newborn fish of livebearers are easier to feed than the fry of egg-laying species, such as characins and cichlids. This makes them much easier to raise, and for this reason, aquarists often recommend them for beginning fish breeder hobbyists.<!-- Minor language changes and clarifications added.--> The larger livebearer fry makes them far less vulnerable to predation, as the parents often eat fry if hungry. With the sufficient cover in the way of plants or porous objects, they can sometimes mature in a community tank.<ref>{{Cite web |title=Livebearers: Raise Guppies, Mollies, Platies & Swordtails in your Aquarium |url=https://www.liveaquaria.com/article/257/?aid=257 |access-date=2022-09-08 |website=www.liveaquaria.com}}</ref> |
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==Ovoviviparous and viviparous fish compared== |
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Most of the Poeciliidae are [[ovoviviparous]], that is, while the eggs are retained inside the body of the female for protection, the eggs are essentially independent of the mother and she does not provide them with any nutrients. In contrast, fish such as splitfins and halfbeaks are [[viviparous]], with the eggs receiving food from the maternal blood supply through structures analogous to the [[placenta]] of [[placental mammals]].<ref>{{Cite book |last=Blackburn |first=D.G. |url=https://www.worldcat.org/oclc/1045069010 |title=Viviparity and oviparity: evolution and reproductive strategies |date=2018 |work=Encyclopedia of reproduction. Volume 1, Male reproduction |others=Michael K. Skinner |isbn=978-0-12-815145-7 |editor-last=Jégou |edition=2nd |location=Oxford |pages=994–1003 |oclc=1045069010}}</ref> |
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==Aberrant livebearers and mouthbrooders== |
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[[Seahorse|Seahorses]] and [[pipefish]] can be defined as livebearers, although in these cases the males incubate the eggs rather than the females. In many cases, the eggs are dependent on the male for oxygen and nutrition so these fish can be further defined as viviparous livebearers. {{Cn|date=April 2021}} |
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Many [[cichlid]]s are [[Mouthbrooder|mouthbrooders]], with the female (or more rarely the male) incubating the eggs in the mouth. Compared with other cichlids, these species produce fewer but bigger eggs, and when they emerge, the fry is better developed and has higher survivability. Because the eggs are protected from the environment but do not absorb nutrients from the parent, this condition is [[Convergent evolution|analogous]] to, though not [[Homology (biology)|identical]] with, ovoviviparity.{{Cn|date=April 2021}} |
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==Livebearer fish gallery== |
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<gallery heights="100px" mode="packed"> |
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Image:Guppy-male.jpg |
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Image:Poecilia latipinna.jpg |
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Image:Poecilia reticulata 01.jpg |
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Image:Xiphophorus helleri 03.jpg |
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Image:Dermogenys sumatrana 02.jpg |
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</gallery> |
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==References== |
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{{Reflist}} |
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==External links== |
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* [http://livebearers.org American Livebearer Association] |
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* [http://www.britishlivebearerassociation.co.uk/ British Livebearer Association] |
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* [https://web.archive.org/web/20060303224019/http://homepage.mac.com/nmonks/aquaria/halfbeaks.html Keeping & Breeding Halfbeaks] Includes growth rate chart and pictures of newborn fish. |
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* [http://thefishdoctor.co.uk/livebearer/maintaining-a-healthy-livebearer-aquarium/ How to Keep Livebearers] |
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[[Category:Ovoviviparous fish]] |
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[[Category:Viviparous fish]] |
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[[Category:Live-bearing fish]] |
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Latest revision as of 21:19, 6 December 2024
Livebearers are fish that retain their eggs inside the body and give birth to live, free-swimming young. They are especially prized by aquarium owners. Among aquarium fish, livebearers are nearly all members of the family Poeciliidae and include: guppies, mollies, platies and swordtails.[1]
The advantages of livebearing to the aquarist are that the newborn juvenile fish are larger than newly-hatched fry, have a lower chance of mortality and are easier to care for. Unusual livebearers include seahorses and pipefish, where the males care for the young, and certain cichlids that are mouthbrooders, with the parent incubating the eggs in the buccal cavity.
Common aquarium livebearers
[edit]Species of interest to aquarists are almost always members of the family Poeciliidae, most commonly guppies, mollies, platies, swordtails, Endler's livebearer, and mosquitofish. Most of these are ovoviviparous, with the developing embryos receiving no nourishment from the parent fish, but a few are viviparous, receiving food from the maternal blood supply. [citation needed]
Because the newborn fish are large compared to the fry of oviparous fish, which are those that lay eggs, newborn fish of livebearers are easier to feed than the fry of egg-laying species, such as characins and cichlids. This makes them much easier to raise, and for this reason, aquarists often recommend them for beginning fish breeder hobbyists. The larger livebearer fry makes them far less vulnerable to predation, as the parents often eat fry if hungry. With the sufficient cover in the way of plants or porous objects, they can sometimes mature in a community tank.[2]
Ovoviviparous and viviparous fish compared
[edit]Most of the Poeciliidae are ovoviviparous, that is, while the eggs are retained inside the body of the female for protection, the eggs are essentially independent of the mother and she does not provide them with any nutrients. In contrast, fish such as splitfins and halfbeaks are viviparous, with the eggs receiving food from the maternal blood supply through structures analogous to the placenta of placental mammals.[3]
Aberrant livebearers and mouthbrooders
[edit]Seahorses and pipefish can be defined as livebearers, although in these cases the males incubate the eggs rather than the females. In many cases, the eggs are dependent on the male for oxygen and nutrition so these fish can be further defined as viviparous livebearers. [citation needed]
Many cichlids are mouthbrooders, with the female (or more rarely the male) incubating the eggs in the mouth. Compared with other cichlids, these species produce fewer but bigger eggs, and when they emerge, the fry is better developed and has higher survivability. Because the eggs are protected from the environment but do not absorb nutrients from the parent, this condition is analogous to, though not identical with, ovoviviparity.[citation needed]
Livebearer fish gallery
[edit]
References
[edit]- ^ David Alderton (15 May 2012). Livebearers: Understanding Guppies, Mollies, Swordtails and Others. CompanionHouse Books. ISBN 978-1-62008-006-1.
- ^ "Livebearers: Raise Guppies, Mollies, Platies & Swordtails in your Aquarium". www.liveaquaria.com. Retrieved 2022-09-08.
- ^ Blackburn, D.G. (2018). Jégou (ed.). Viviparity and oviparity: evolution and reproductive strategies. Michael K. Skinner (2nd ed.). Oxford. pp. 994–1003. ISBN 978-0-12-815145-7. OCLC 1045069010.
{{cite book}}:|work=ignored (help)CS1 maint: location missing publisher (link)
External links
[edit]- American Livebearer Association
- British Livebearer Association
- Keeping & Breeding Halfbeaks Includes growth rate chart and pictures of newborn fish.
- How to Keep Livebearers