Livebearers are aquarium
fish
Fish are aquatic, craniate, gill-bearing animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish as well as various extinct related groups. Approximately 95% of li ...
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
The Poeciliidae are a family of freshwater fishes of the order Cyprinodontiformes, the tooth-carps, and include well-known live-bearing aquarium fish, such as the guppy, molly, platy, and swordtail. The original distribution of the family was t ...
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 List of freshwater aquarium fish species, freshwater aquarium fish species. It is a member of the ...
,
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 ...
s.
The advantages of livebearing to the aquarist are that the newborn
juvenile fish
Fish go through various life stages between fertilization and adulthood. The life of a fish start as spawned eggs which hatch into immotile larvae. These larval hatchlings are not yet capable of feeding themselves and carry a yolk sac which ...
are larger than newly-hatched fry, have a lower chance of mortality and are easier to care for. Unusual livebearers include
seahorse
A seahorse (also written ''sea-horse'' and ''sea horse'') is any of 46 species of small marine fish in the genus ''Hippocampus''. "Hippocampus" comes from the Ancient Greek (), itself from () meaning "horse" and () meaning "sea monster" or " ...
s 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 se ...
, 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
The Poeciliidae are a family of freshwater fishes of the order Cyprinodontiformes, the tooth-carps, and include well-known live-bearing aquarium fish, such as the guppy, molly, platy, and swordtail. The original distribution of the family was t ...
, 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 List of freshwater aquarium fish species, freshwater aquarium fish species. It is a member of the ...
,
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 ...
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
The western Mosquitofish (''Gambusia affinis'') is a North American freshwater fish, also known commonly, if ambiguously, as simply Mosquitofish or by its generic name, ''Gambusia'', or by the common name gambezi. Its sister species, the east ...
. Most of these are
ovoviviparous
Ovoviviparity, ovovivipary, ovivipary, or aplacental viviparity is a term used as a "bridging" form of reproduction between egg-laying oviparous and live-bearing viviparous reproduction. Ovoviviparous animals possess embryos that develop insi ...
, with the developing embryos receiving no nourishment from the parent fish, but a few are
viviparous
Among animals, viviparity is development of the embryo inside the body of the parent. This is opposed to oviparity which is a reproductive mode in which females lay developing eggs that complete their development and hatch externally from the m ...
, receiving food from the maternal blood supply.
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 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
Ovoviviparity, ovovivipary, ovivipary, or aplacental viviparity is a term used as a "bridging" form of reproduction between egg-laying oviparous and live-bearing viviparous reproduction. Ovoviviparous animals possess embryos that develop insi ...
, 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
Among animals, viviparity is development of the embryo inside the body of the parent. This is opposed to oviparity which is a reproductive mode in which females lay developing eggs that complete their development and hatch externally from the m ...
, with the eggs receiving food from the maternal blood supply through structures analogous to the
placenta
The placenta is a temporary embryonic and later fetal organ that begins developing from the blastocyst shortly after implantation. It plays critical roles in facilitating nutrient, gas and waste exchange between the physically separate mater ...
of
placental mammals
Placental mammals (infraclass Placentalia ) are one of the three extant subdivisions of the class Mammalia, the other two being Monotremata and Marsupialia. Placentalia contains the vast majority of extant mammals, which are partly distinguishe ...
.
Aberrant livebearers and mouthbrooders
Seahorse
A seahorse (also written ''sea-horse'' and ''sea horse'') is any of 46 species of small marine fish in the genus ''Hippocampus''. "Hippocampus" comes from the Ancient Greek (), itself from () meaning "horse" and () meaning "sea monster" or " ...
s 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 se ...
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
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 ...
, 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 ( ...
to, though not
identical
Two things are identical if they are the same, see Identity (philosophy).
Identical may also refer to:
* ''Identical'' (Hopkins novel), a 2008 young adult novel by Ellen Hopkins
* ''Identical'' (Turow novel), a 2013 legal drama novel by Scott T ...
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 AssociationBritish Livebearer AssociationIncludes growth rate chart and pictures of newborn fish.
How to Keep Livebearers
Aquariums
Ovoviviparous fish
Viviparous fish
Live-bearing fish