Cyprinodontiformes vivíparos e ovovivíparos
Livebearer Cyprinodontiformes
Espécies > Ficha da espécie > Xiphophorus maculatus
Species > Species profile > Xiphophorus maculatus
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Cyprinodontiformes vivíparos e ovovivíparos Livebearer Cyprinodontiformes Espécies > Ficha da espécie > Xiphophorus maculatus Species > Species profile > Xiphophorus maculatus |
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Adult male : 20 a 40.4 mm Adult female : 50.1 a 60.2 mm
Caudal fin rays : / 20 ( 22 ) Scales on lateral line : 25 ( 27 ) Head lenght body lenght ratio ( male ) : 0,24 Head lenght body lenght ratio ( female ) : 0,20
Northern limits are at Jamapa river drainage, in Vera Cruz State and it extends right to Petén District in Guatemala, besides a vast area of Belize. As a rule, in hydrographical basins on the far North locations, ( Jamapa, Cotaxtla, Otopa, Blanco, Tonto, Papaloapan, Coatzacoalcos San Juan, Dos Canos ), the species is established only in altitudes below 500 metres over the sea. On the species geographical distribution vast area we found predominantly sub-humid to humid climates ( rainy sub-tropical and tropical ). Vera Cruz city is located precisely near the northern limit. Medium air temperatures are around 20ºC ( 68.0ºF ) in January and 27ºC ( 80.6ºF ) in June. Even so, this will never demonstrate in evidence the real local weather. The hottest month in the region isn’t June but instead April, May or even September, according to the place we are talking about. Standard water temperatures can be 0.4ºC ( 0.72ºF ) higher in August than in June. When the year’s peak hottest days take place in April, for instance, we are talking about regions located at latitudes where the Sun is straight up at that moment and raining season is still on the way. Around May or so, as soon as the first seasonal heavy precipitations get there, cloudy sky as well as rain “ freshness “ let the values get, somehow, a bit downwards with reference to April. Even so, while maximum daily heat fall a little, minimum lowers tender to rise due to overcast skies above at night. By this same reason, in some other areas in the region, August or even September can show the highest records, ( eventually caused by the clearest skies after the heaviest rains ). Down South, average annual temperatures can show a discrepancy of only 0.5ºC ( 0.9ºF ) between winter and summer ( January/July ). In Belize topmost air temperatures are 10ºC ( 50.0ºF ) and 35ºC ( 95.0ºF ). Year average is around 26ºC ( 78.8ºF ) with lower temperatures generally above 18ºC ( 64.4ºF ), even during colder winter months. Water thermal values in such vast area can vary considerably. Typical locations can experiment something flanked by 24ºC ( 75.2ºF ) and 30ºC ( 80.6ºF ) between April and October, as well as something flanked by 16ºC ( 60.8ºF ) and 24ºC ( 75.2ºF ) from November to March. In Southern most parts, water temperature can stand stuck between 19ºC ( 66.2ºF ) and 26ºC ( 78.8ºF ) all year round. Xiphophorus maculatus look for best habitat in rivers, channels, streams, brooks and rivulets, in particular when they are slow runners. This species is also common in lakes, coastal lagoons as well as in some other lentic environments. Usually the Platy wild populations are found in sandy bottoms, some sub-aquatic vegetation and even underwater dead trees. On average they are found close to the shore in shoals, or near well planted sand banks of the larger streams. The species also look for underwater tree roots on weedy shorelines, where specifically young fish and fry search for refuge from predators. Smaller water bodies including brooks are also very well-liked; in particular if they are slow running. Adults can take their chances in deeper open waters around 50 centimetres, but usually avoid profundities of more than 1 meter. Wild environment offers clean transparent water almost the time, but on the raining season opaque and low visibility flow can suddenly wash them many kilometres away. In may locations pH values vary around 7,5 and 8,1 or sometimes a little bit more. 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.
Tolerated limits : 16ºC ( 60.8ºF ) e 34ºC ( 77.0ºF ) Survival limits : 12ºC ( 53.6ºF ) e 36ºC ( 96.8ºF ) Ideal pH : 7 – 8.2 Ideal dH : 9º - 19º Maximum salinity : 1,021 ( 28,5 ppt )
Maybe in result of environmental as well as predatory pressure isn’t very expectable to find in the wild males as large as in captivity. Even so, wild populations from several species under strict close contact with predators do show evidence of larger individuals, specially when compared with those others free from such stress, ( and this one is far from be an exception to this rule ). Thanks to a quite wide geographical distribution, we can find some interesting biological as well as morphological differences between Platy populations. That’s what we can conclude from a paper from 1977 - “ A Sex-Linked Gene Controling the Onset of Sexual Maturity in Female and Male Platyfish ( Xiphophorus maculatus ), Fecundity in Females and Adult Size in Males “ from Klaus D. Kallman and Valerie Borkoski. On this interesting document one can find that a variety of populations show quite interesting divergent performance in terms of sexual maturity and fecundity. Depending mainly on genetic inheritance, both Xiphophorus maculatus ( male and female ) achieve adulthood between 5 and 73 weeks of age, ( Kalman e Borkoski, 1977 ). Off course we are taking in contemplation fish from different populations but kept under the same background in laboratory. It’s obvious that temperature, feeding and other conditions can become quite influent on this matter. While still immature, both sex young animals show equivalent growth. As in many other Poeciliinae species, males almost stop body development after attaining sexual maturity, so those who attain primary sexual characters first have a propensity to be smaller in size contrasting with later adulthood ones. On the supra cited paper, males from different populations under same environment conditions were studied concerning adult size. While in one of the studied populations full development took place next to 8 weeks of live and about 21 mm of size, several others had similar occasion just between 11 to 13.5 weeks, measuring from 25 to 29 mm. On the reverse top it was one of the populations were males reach sexual maturity only around 26.5 weeks, attaining a size of 37 mm or so, ( Kalman e Borkoski, 1977 ). Another interesting difference among populations can be found between those who live in Mexican waters and those who came from Belize. For the reason that there are three sex chromosomes identified by science in most natural populations, ( W, X and Y ), the sex genotype of females can be either WY, WX or XX and that of males can be XY, or YY, ( Kallman 1973 ). By genotype one must be aware of the specific genetic makup ( or specific genome ) of an individual in a form of DNA. On these wild populations in particular, there are two identified types of sex-determining mechanisms. In Xiphophorus maculatus of northern distribution, the male is heterogametic ( XX female, XY male ), while in those from Belize is the female ( WY female, YY male ), ( Mac Intyre, 1961 ). Along with other species inside the Xiphophorus genus, Platy is also reported in numerous sources regarding spontaneous sex reversal ( an individual who is functionally from one sex, but genotypically from the other ). This is not at all a frequent occurrence. Most of the cases take place in domesticated strains of unknown ancestry which have been bred by hobbyists or dealers. Such strains usually include interracial or interspecific hybrids and are thus of questionable value in scientific studies. It is simply a very popular myth and there is no accuracy at all on the accepted judgement that if you keep only females in a tank, sooner or later one of them will become a male as well as vice-versa for males too. Natural nourishment of this species is the omnivorous kind. Beck in the wild, these fish consume almost all little live prey of convenient size, especially zoobentos and zooplankton, aquatic invertebrates, insects as well as a lot of vegetable stuff ( particularly detritus and algae ). Captivity feeding does not offer any problems. Xiphophorus maculatus tolerate very well dry food ( flake ), freeze-dried, frozen, fresh aquarium fish food or live prey for most spectacular results. 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. Infrequently, once in a blue moon, you can use row meet from cow, pork, rabbit or birds, without any fat at all. This is a continuous breeding season kind species. While temperatures still remain under ideal values and photo-period allows it, they reproduce incessantly. Cannibalistic conduct in captivity can be considered has a noticeable alarm indication. This may mean that we are in presence of nourish lacking, or in particular a sign of some diet constitution disturbance as well as inadequate composition. In small tanks without enough sheltering, hungry or incorrectly feed parents, in particular when as a rule they see new born like prey, obviously these fish will fallow basic survival instincts. Anyway, we are talking about a considerably prolific species. A Platy female can spend something from 26 to 29 days between deliveries. This period is interrelated with temperature and feeding above all. First births can be very irregular in young females. Usually an interlude from 27 to 90 days is more expectable than a regular start. Fertilization takes place about a week after delivery. Females subjected to maternity cages will face permanent agony and suffering. They can refuse to give birth for long periods. On the other hand, a great amount of newborn under these conditions will face complications or even be expelled death by the mother. A birth can result ultimately in a total between 20 and 40 newborn in younger females and something around or little more than 60 in full developed ones. With age, older females will become reproductively more instable and the gestations tender to become irregular and to look a lot like the initial cycles. Several cases of sterility in females of this species have been also reported. We speculate if this isn’t caused by internal reasons, presumably some physiological occurrence like ovary degeneration or something like that. Animals affected by this health problem keep going apparently well and can have a normal longevity, but they can’t breed. Feeding newborn and fry will be no particular problem at all. This species will fallow usual needs from other members of Poeciliinae sub-family.
Expected, but on the odd occasion, male disputes don’t harm other fish around, and exceptionally can result in injuries to the antagonists itself. 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 you pay attention to your aquarium inhabitant’s of this genus, please don’t forget their relative’s important role at cancer hereditarily studies.
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.
For further knowledge or information about this please check Livebearer Cyprinodontiformes in the IUCN Red List of Threatened Species.
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