Cyprinodontiformes vivíparos e ovovivíparos

Livebearer Cyprinodontiformes

Espécies > Ficha da espécie > Xiphophorus variatus

Species > Species profile > Xiphophorus variatus

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I - Morphology Synopsis ( some meristic characters )

Total absolute lenght

Adult male : 39 a 56.4  mm

Adult female : 59 a 71 mm

Dorsal fin rays : / 10 ( 12 )

Caudal fin rays : / 20 ( 22 )

Scales on lateral line : 25 ( 26 )

Head lenght body lenght ratio ( male ) : 0,19

Head lenght body lenght ratio ( female ) : 0,23

II - Habitat and Geographical distribution

Variegated Platy wild populations can be found from Southern Tamaulipas State to Northern Vera Cruz State in Mexico.

Due to its location as well as orography, this region is under an interesting climate typology broad range.

Inside the species geographical distribution, it’s possible to find tropical humid to sub-humid classic weather at coastal areas and temperate from sub-humid to draw in higher altitudes.

Mountain edges and pronounced slope terrains limit the species abundance due to water running flow.

Larger rain fall period take place in summer and from June to October hurricanes can occur.

Xiphophorus variatus can be found in rivers, streams and rivulets. While warmest surface of running water is one of preferred environments, we can also locate many populations in lentic surroundings like swamps, lakes and lagoons.

In all wild biotopes these fishes show an evident preference for dense under water vegetation proximity and as a rule they form schools in the vicinity of shore, mainly composed by young and fry.

Adults are more assiduous in deeper background, despite the fact that they remain more often close to 50 cm or less.

In other human made introduction new locations of this specie in some countries throughout the world, we can find establish populations on the same kind of surroundings. In temperate or cooler regions some introduced populations seek refuge from lower temperatures, during winter months, in thermal habitats, avoiding this way an assured fatality by cold narcosis.

III - Physical-chemistry parameters

Ideal temperature range : 17ºC ( 62.6ºF ) - 26ºC ( 78.8ºF )

Tolerated limits : 13ºC ( 55.4ºF ) e 32ºC ( 89.6ºF )

Survival limits : 8ºC ( 46.4ºF ) e 36ºC ( 96.8ºF )

Ideal pH : 7 – 8.3

Ideal dH : 9º - 19º

Maximum salinity : 1,011 ( 15,4 ppt )

Temperature annual maintenance for this species in captivity ( suggestion ) :
 

IV - Biology and ecology synopsis

Xiphophorus variatus wild population’s males seemed to be quite variable, especially in body length and colouration.

This interesting diversity found in wild males can eventually be related to genetic polymorphism or even social mechanisms.

In fact, under some circumstances and specific conditions, young male’s maturity can experience a deferral when larger adult ones are present in the group. This process can even lead to sexual mature inhibition for a quite notable period when pressure is high.

In larger populations this delay can be minimum or inexistent. On these generously proportioned communities another phenomenon can take place; synchronized male’s sexual maturation.

There is a genetically secluded relation between age and size for maturity on each male. Individual progression right the way through this important and decisive biological stage of live is however, by this fact, much correlated with personal heritage. Like in many other species on this family, male’s growth stops or reduces significantly after maturity, so details like these aren’t difficult to determine.

According to several scientific works, improved reproductive success is achievable by larger males. Lower sized ones get some accomplishment by sneaky mating procedures getting females by surprise, while larger competitors frequently make use of exhibition rituals prior to copulation.

Apparently females of this specie do care and accept by far more generously proportioned partners.

Wild Variable Platy feed on almost living organism of convenient dimensions, predominantly zoobentos and zooplankton, besides vegetal matter assortment ( aquatic plant debris in particular ), algae as well as insects.

Captivity feeding does not offer any problems.

These fishes tolerate very well dry, freeze-dried, frozen, fresh aquarium fish food or live prey.

The use of same diet than other popular Livebearer species is proper without any special complement or concern.

Flake foods are very well accepted but, if possible, always include also brine shrimps, mosquito larvae, blood worms, tubifex, daphnia, ( alive or frozen ).

You can add also milled row, fish or molluscs from about all kinds used on human diet.

Back in nature, these fishes are gregarious and form schools with both sex animals of different ages together under a structured hierarchy.

Females spend most time foraging, while males dedicate a great deal of their time to demonstrations, some fights but predominantly to attempt mating.

In some places groups can attain large numbers, although usually is more common to come across with 30 to 40 adults ( 7 to 10 males and 25 to 35 females ), surrounded by an indistinct amount of immature fishes in different stages of development. These groups are in evidence not far from shore, when best protection and food abundance can provide them a good choice to carry on and to face predation.

These kinds of behaviour or interactions are quite adulterated in aquarium, due to space limitations, artificial habitat availability, number of own specie members present, predation absence and interactions with other species included on each specific tank community.

Outdoors garden pond groups however can return to an embryonic natural behaviour, sometimes very close to the wild ancestrally. This will take place in particular if certain habitat conditions are taken in consideration.

Cannibalistic behaviour on newly birth fry is common according more than one testimony. As we can expect in restrained spaces like in smaller thanks, without proper vegetation cover to provide shelter and mainly when adults are inadequately feed, this will be in fact common.

Nevertheless this is usually a prolific specie.

Variable Platyfish female’s gestation lasts between 4 and 7 weeks, depending on temperature and food.

A birth can produce from 15 to 20 fry in young females and 50 to something more in full-developed ones.

Fry feeding fallows usual Poeciliinae Sub-Family needs and procedures.

V - Complementary notes

By early 1920’s it starts to become evident that crosses inside Xiphophorus genus were quite undemanding. What was new by the time that hobbyists get in contact with the first hybrids was the impressive number of combinations that could originate fertile offspring as well as progeny from both sexes.

These occurrences are so usual that is even advisable to keep these species apart and never let them cohabit in the “ small “ space of a domestic tank.

Cross births include generally both parental species perceptible contributions and intermediate bodily appearance is typical.

By the above-mentioned facts, these F1 hybrids and their descendants do allow that some sort of distinctions from one, or from both parental species, can be genetically fixed with no trouble. In some special situations, a number of characteristics from one of the two progenitors arise more strongly than never at these hybrid descendants.

That is the case of melanoma, one of the most deadly health disorders, commonly known as the skin cancer. So evident was this happenstance that starts do earn particularly scientist’s attention in USA and Germany since little after of first crosses.

These fish melanoma is some how related to melanic marks very common in certain strains and among some hybrids in particular.

As we could expect, such prevalence of the disease on these extraordinary small lab partners, soon develop into a quite obvious talented work filed for scientists at cancer investigation.

Since than, some models have become popular, and these species in particular turn out to be extremely useful instruments on the study of melanoma mechanisms and progression.

An incredible coincidence is that, remarkably, fish pigmented cells vulnerable to the disease are morphologically, physiologically and in biochemical terms, quite similar to human cells.

Investigation methodology used with Xiphophorus also include radiations, providing scientists a perspective about how this kind of cancer evolutes as well as it incidence.

Right the way through subsequent genealogy of laboratory manipulated fishes; investigations can expose a great deal of melanoma progress from generation to generation by means of genetic anticipation.

Next time youpay attention to your aquarium inhabitant’s of this genus, please don’t forget their relative’s important role at cancer hereditarily study.

VI - Threats, protection and present status

Environment contamination by domestic and industrial wastewater dumping in to nature, aquatic resources use above levels that precipitation can re-establish for agriculture, industrial or human consumption, as exotic species introduction are the great threats that Xiphophorus variatus is facing at present in some locations of wild distribution.

The specie conservation status is not an issue for concerning at the moment and it is not in the I.U.C.N. Red List.

memorandum about the Xiphophorus Genus : Regarding more or less 29 species placed on it, 1 ( Xiphophorus clemenciae ) is classified as data deficient,  also 1 ( Xiphophorus couchianus ) is classified as critically endangered and 2 ( Xiphophorus gordoni and Xiphophorus meyeri ) are classified as endangered.

For further knowledge or information about this please check Livebearer Cyprinodontiformes in the IUCN Red List of Threatened Species.

Other topics available about this species :

Xiphophorus Interspecies Hybrids as Genetic Models of Induced Neoplasia

http://dels.nas.edu/ilar_n/ilarjournal/42_4/xiphophorus.pdf

Ronald B. Walter and Steven Kazianis

ILAR Journal  Volume 42, Number 4 2001