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Livebearers are aquarium fish that retain the eggs inside the body and give birth to live, free-swimming young. Among aquarium fish, livebearers are nearly all members of the family Poeciliidae and include
guppies The guppy (), also known as millionfish and rainbow fish, is one of the world's most widely distributed tropical fish and one of the most popular freshwater aquarium fish species. It is a member of the family Poeciliidae and, like almost all ...
, mollies,
platies Platy is a common name of freshwater fish in the genus ''Xiphophorus'' that lacks a "sword" at the bottom of their tails. Both species are livebearers, similar to other fish of the family Poeciliidae, such as the guppy and molly. Platies are nat ...
and
swordtail ''Xiphophorus'' is a genus of euryhaline and freshwater fishes in the family Poeciliidae of order Cyprinodontiformes, native to Mexico and northern Central America. The many ''Xiphophorus'' species are all known as platyfish (or platies) and ...
s. 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 Pipefishes or pipe-fishes (Syngnathinae) are a subfamily of small fishes, which, together with the seahorses and seadragons (''Phycodurus'' and ''Phyllopteryx''), form the family Syngnathidae. Description Pipefish look like straight-bodied seah ...
, where the males care for the young, and certain
cichlid Cichlids are fish from the family Cichlidae in the order Cichliformes. Cichlids were traditionally classed in a suborder, the Labroidei, along with the wrasses ( Labridae), in the order Perciformes, but molecular studies have contradicted this ...
s that are
mouthbrooder Mouthbrooding, also known as oral incubation and buccal incubation, is the care given by some groups of animals to their offspring by holding them in the mouth of the parent for extended periods of time. Although mouthbrooding is performed by a va ...
s, with the parent incubating the eggs in the
buccal cavity The buccal space (also termed the buccinator space) is a fascial space of the head and neck (sometimes also termed fascial tissue spaces or tissue spaces). It is a potential space in the cheek, and is paired on each side. The buccal space is super ...
.


Common aquarium livebearers

Species of interest to aquarists are almost always members of the family Poeciliidae, most commonly
guppies The guppy (), also known as millionfish and rainbow fish, is one of the world's most widely distributed tropical fish and one of the most popular freshwater aquarium fish species. It is a member of the family Poeciliidae and, like almost all ...
, mollies,
platies Platy is a common name of freshwater fish in the genus ''Xiphophorus'' that lacks a "sword" at the bottom of their tails. Both species are livebearers, similar to other fish of the family Poeciliidae, such as the guppy and molly. Platies are nat ...
,
swordtail ''Xiphophorus'' is a genus of euryhaline and freshwater fishes in the family Poeciliidae of order Cyprinodontiformes, native to Mexico and northern Central America. The many ''Xiphophorus'' species are all known as platyfish (or platies) and ...
s,
Endler's livebearer ''Poecilia wingei'', known to aquarists as Endlers or Endler's livebearer, in the genus ''Poecilia'', is a small fish native to the Paria Peninsula in Venezuela. They are prolific breeders and often hybridize with guppies. These very colorful hy ...
, and mosquito fish. 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. Because the newborn fish are large compared to the fry of
oviparous Oviparous animals are animals that lay their eggs, with little or no other embryonic development within the mother. This is the reproductive method of most fish, amphibians, most reptiles, and all pterosaurs, dinosaurs (including birds), and ...
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 size of livebearer fry makes them far less vulnerable to predation, as the parents often eat fry if hungry. With sufficient cover in the way of plants or porous objects, they can sometimes mature in a community tank.


Ovoviviparous and viviparous fish compared

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.


Aberrant livebearers and mouthbrooders

Seahorses and
pipefish Pipefishes or pipe-fishes (Syngnathinae) are a subfamily of small fishes, which, together with the seahorses and seadragons (''Phycodurus'' and ''Phyllopteryx''), form the family Syngnathidae. Description Pipefish look like straight-bodied seah ...
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. Many
cichlid Cichlids are fish from the family Cichlidae in the order Cichliformes. Cichlids were traditionally classed in a suborder, the Labroidei, along with the wrasses ( Labridae), in the order Perciformes, but molecular studies have contradicted this ...
s 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 are better developed and have a higher survivability. Because the eggs are protected from the environment but do not absorb nutrients from the parent, this condition is
analogous Analogy (from Greek ''analogia'', "proportion", from ''ana-'' "upon, according to" lso "against", "anew"+ ''logos'' "ratio" lso "word, speech, reckoning" is a cognitive process of transferring information or meaning from a particular subject (t ...
to, though not identical with, ovoviviparity.


Livebearer fish gallery

Image:Guppy-male.jpg Image:Poecilia latipinna.jpg Image:Poecilia reticulata 01.jpg Image:Xiphophorus helleri 03.jpg Image:Dermogenys sumatrana 02.jpg


References

{{Reflist


External links


American Livebearer Association

British Livebearer Association


Includes growth rate chart and pictures of newborn fish.
How to Keep Livebearers
Aquariums Ovoviviparous fish Viviparous fish Live-bearing fish