Guppy

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Guppy

For other uses of this word, see Guppy (disambiguation).

The guppy, also known as guppie (Poecilia reticulata) is one of the most popular freshwater aquarium fish species in the world. It is a small member of the Poecilidae family (females 3 centimetres long, males 2 centimetres long) and like all other members of the family, is live-bearing. It prefers a hard water aquarium and can withstand levels of salinity up to 150% sea water (58 ppt sodium chloride)Chervinski, J. (1984) Salinity tolerance of the guppy, Poecilia reticulata Peters. Journal of Fish Biology 24: 449-452., which has led to them being occasional included in marine tropical community tanks, as well as more usually in freshwater tropical tanks. Its most famous characteristic is its propensity for breeding.

Taxonomy

Robert John Lechmere Guppy (1836-1916) discovered this tiny fish in Trinidad in 1866, although the fish was known to German aquarists prior to that time.

Over time, many species are assigned a different taxonomic name. The guppy is no exception:

Lebistes reticulatus
Acanthocephalus guppii
A. reticulatus
Girardinus guppii
G. petersi
G. poeciloides
G. reticulatus

Haridichthys reticulatus
Heterandria guppyi
Lebistes poecilioides
Poecilia poeciloides
Poecilioides reticulatus.
Currently: Poecilia reticulata

Distribution and diversity

In its natural environment in South America and the Caribbean, guppies are often found as isolated breeding populations. In its native range, the guppy can be found in small streams and ponds of virtually any size. In Trinidad they are colloquially known as "millions" because of their fecundity.

In many countries with tropical, subtropical and mediterranea climates where guppies were not originally present, they have escaped from captivity and established naturally breeding ("feral") populations. It has also been introduced to some areas to keep down the mosquito population and help fight malaria, usually with mixed or negative results to the local ecosystem.

Physical description

The female guppy is drab brown to grey in colour. The somewhat smaller male naturally has a colourful caudal fin (tailfin), showing wide variety in the wild, depending on where the stock comes from. These colourful variations have been considerably enhanced in shape and colour by selective breeding.

Ecology and behaviour

There is a great deal of variety between the populations, many with distinctive coloring or patterning. Those that live in habitats where predators are common tend to be less vividly decorated. Populations that deal with fewer predators are much more colorful. Recent studies suggest that vividly colored males are favored via sexual selection while natural selection via predation favors subdued tones. As a result, the dominant phenotypes observed within a reproductively isolated community are a function of the relative importance each factor has in a particular environment.

Occasionally male guppies may behave aggressively towards each other, engaging in fin-nipping and other bullying behaviour. This behaviour is also sometimes exhibited towards other top swimmers like platys and swordtails and occasionally other fish with prominent fins such as angelfish.

Guppies live in complex networks, choosing social partners and remembering them. Croft, D. P., J. Krause and R. James (2004) Social networks in the guppy (Poecilia reticulata). Proceedings of the Royal Society of London Biology Letters 271: 516-519..

The extensive work on guppies is summarised in Anne Magurran's Evolutionary Ecology: the Trinidadian guppy.

As a pet

Guppy breeding by aquarists produces variations in appearance ranging from color consistency to fantails and "spike" swordtails. Selective breeding has created an avid "fancy guppy" collector group, while the "wild" guppy maintains its popularity as one of the hardiest aquarium fish. The gestation period of a guppy is 22-26 days. When the female guppy becomes fertilized, a dark area near the anus, known as the gravid spot, will enlarge and darken. Guppies prefer water temperatures of about 72°F (22°C) for reproduction. After giving birth, the female is ready for conception within a few hours. If a male does not mate with the female soon after birth, the female can use stored sperm from the previous mating.

For people breeding their own guppies, be aware that the adults will eat their young. Specially designed livebearer birthing tanks, which can be suspended inside the aquarium, are available from aquatic retailers. These serve the dual purpose of shielding the pregnant female from further attention from the males, and of providing a separate area for the newborn young as protection from being eaten by their mother.

Another option for aquarists is to simply provide lots of plants for the young to hide in. Immediately after giving birth, female guppies experience a rush of hormones which serve to decrease their appetites. This can last up to 12 hours, which provides young ample time to hide provided that no other adult fishes are around.

References