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Амека

Амека (латAmeca splendens), вид живородящих рыб семейства Гудиевые (Goodeidae). В природе была распространена в бассейнах горных рек на территории Мексики (р. Рио-Амека, р. Рио-Теу-Хитлан и др.), но в 1996 году ей был присвоен статус исчезнувшей в дикой природе.

А. имеет высокое, сжатое по бокам тело. Она очень подвижна. Самки крупные, 10—12 см, серебристого цвета с черными крапинками по всему телу. Самцы мельче, 6—8 см, с зеркально-блестящими чешуйками, хвостовой плавник самца оторочен чёрно-жёлтым кантом. В утренние часы по всему телу рыб, от глаз до хвостового плавника, проявляется чёрная полоса, которая при ярком освещении исчезает или становится еле заметной. 

Орган спаривания у самцов (псевдофалус) развился в результате преобразования передней части анального плавника, в то же время задняя часть плавника осталась без изменений. Внутриутробное питание и газовый обмен у эмбрионов осуществляется за счет своеобразных плацентарных нитей — трофотений, соединенных ворсинками со слизистой оболочкой яичников. У новорожденных рыб трофотении видны некоторое время, но затем они исчезают.


Ameca splendens, a bony fish from the monotypic genus Ameca of the splitfin family (Goodeidae), is commonly known as the Butterfly Goodeid orButterfly Splitfin. It was formerly found throughout the Ameca River drainage in Mexico; the type locality is Rio Teuchitlán in the vicinity of Teuchitlán,Jalisco. The species was only ever found in an area about 10 miles (15 km) in diameter. 

Today, the species is rated as extinct in the wild by the IUCN, though it is noted that this assessment is obsolete: a remnant population has been found to persist in El Rincón waterpark near the town of Ameca. Possibly, it also exists in a feral state in the USA; individuals apparently derived from escaped or introduced captive stock were met with in southeastern Nevada.  For some time, it was a popular fish among aquarists, but unfortunately hobbyist stocks have declined quite a lot more recently, placing its survival in jeopardy.

As its common name implies it is indeed quite an attractive fish. A dominant mature male specimen will have a large dorsal fin which like the caudal fin is washed with black. A yellow band stretches along the caudal's back margin. The body of both sexes is ochre, with silvery sides and a brownish back, which in males usually have numerous glittering metallic scales. Females and immatures having black dots on the sides and ochre fins. The fins of males intensify in color when they are excited, and depending on their mood, they can show more or less strongly a black band along the side. For the first two weeks or so after birth, the young are entirely silvery. 

Males can also be told apart from females because they have the anal fin's front part split off and transformed to a blunt, flexible andropodium used for mating. As usual in live-bearers, males are the smaller sex, reaching some 3 in (7–8 cm) total length at best, with females being able to grow up to 4 in (10 cm) TL under good conditions.  

In its former natural habitat, the bedrock is limestone, resulting in a hard and alkaline water with a general hardness of 6-10 dGH, while the temporary (carbonate) hardness is usually between 7 and 11 degrees. The pH is around 8, and temperature varies little between the seasons but ranges between about 70-85°F (20-30°C) between day and night. The vegetation is largely limited to algae and Ceratophyllum hornworts. The remnant wild population coexists with the native Blackfin Goodea (Goodea atripinnis) and Lerma Livebearer (Poeciliopsis infans), as well as with the Common Molly (Poecilia sphenops), Oreochromis tilapias and the Bluegill(Lepomis macrochirus) which presumably have all been introduced. 

Among groups of A. splendens, a loose dominance hierarchy will develop, in particular in confined environments. Males chase each other about, with the dominant male(s) showing the most splendid coloration. Submissive males will try to retreat from attacks, typically towards the surface, and may shake their head as a calming signal. 

Like other Goodeidae, Butterfly Splitfins mate by internal fertilization and spawn fully developed young. The females become sexually mature at about 6 months of age and can give birth every 6 to 10 weeks according to the water temperature and the condition of the fish. Mating is preceded by a courtship, where the males present themselves to the females with their head pointing downwards – up to 45° from horizontal – and shake the forward part of their body. In that respect, they resemble the Jeweled Splitfin (Xenotoca variata); they do not have a ritualized "courtship dance" as some other splitfins, but the male will sometimes rotate to present either flank to the female. The females respond by shaking their head. 

The fry when born can be up to 0.8 in (20 mm) in length, as the females feed the unborn young via trophotaenia which have a similar function as the umbilical cord in humans.  

The Butterfly Goodeid has a somewhat exaggerated reputation of being a fin nipper,[weasel words] but being a large and robust fish, it will certainly bully small and delicate species like guppies or smalltetras. When housed with less tender species that require similar conditions, it is a great fish for any tank type; even the hardier species of Apistogramma and similar dwarf cichlids make good companions, with water parameters compromising between the splitfins' and the cichlids' requirements at a point similar to most tap water. 

A. splendens thrive best in clean, well aerated water, at temperatures in the 70°Fs (20-25°C) and neutral or slightly higher pH, with water hardness between 5 and 10 degrees dGH composed mainly from calcium hardness. They do not tolerate overly low pH and too soft water well, and are unsuitable for dedicated rainforest aquaria with low pH and almost-zero hardness (e.g. for most tetras ordanionins). Butterfly goodeids are strong swimmers and social fish; they like to be dwell in groups of 3-5 males and 3-7 females in large tanks (50 gal/200 L and up) where they can grow to full size. In smaller tanks of 15 gal (60 L) and up they will stay smaller, and fewer individuals or no other fish should be kept. They do not uproot vascular plants, and although they will every now and then take a bite from tender leaves if not fed sufficient vegetable food, their overall effect on plant growth is beneficial as they keep down algae and clean off detritus. A. splendens will breed quite readily in the aquarium; some floating plants such as Ceratopteris or Ceratophyllum will provide protection for young fry.

Aggressiveness varies with population density; at high population densities, tank decoration is highly significant in influencing behavior. It is noted that at least among the captive population, Butterfly Splitfins become more aggressive if there is much decoration in the tank. It may be that this trait has actually become genetically fixed, since no wild fish have been added to the captive stock for decades: aggressive males are liable to mate more often in tanks that have hiding places, while in the wild a harassed individual will simply swim away, and in a sparsely decorated tank less aggressive males will not find it much harder to mate than those males that relentlessly pursue females even if these hide. Thus, a fishkeeper wanting to provide A. splendens with optimal conditions will not spend much money on extensive tank decoration but rather on a large tank; a bunch of floating plants and a few smooth and nicely colored rocks are entirely sufficient as decoration and in fact closely resemble the natural habitat of this species. 

Butterfly Splitfins are if anything rather voracious, they will happily eat most sorts of commercial frozen, freeze-dried, flake or tablet fish food.  They gladly take live prey up to the size of week-old guppy fry, but really need a healthy dose of plant material, ideally green algae, to thrive. They are, in fact, ideal algae eaters for tanks with small, hard-water cichlids. If not enough algae are available,organic vegetables such as pieces of lettuce, chunks of frozen chopped spinach or a few mashed green peas are recommended additions to the diet. Fry do not need "baby" food such as brine shrimpnauplia, though as in adults, plant food will increase growth and vitality.

Lighting should be strong, to encourage growth of algae; direct sunlight is ideal. In summer, they can be kept in outside tanks, basins or small ponds in temperate and warmer areas – they can tolerate overnight air temperatures of 60°F (15 °C) well enough –, but should be protected from birds, cats and other predators.

References:

  • Contreras-Balderas, S. & Almada-Villela, P. (1996). Ameca splendens. 2006. IUCN Red List of Threatened Species. IUCN 2006. www.iucnredlist.org. Retrieved on 29 November 2006.

  • Fuller, Pam (2006): Ameca splendens. USGS Nonindigenous Aquatic Species Database. Gainesville, FL. Revision Date: 12/5/2003. Retrieved 2006-NOV-09.

  • Kelley, J.L.; Magurran, A.E. & Macías García, C. (2006): Captive breeding promotes aggression in an endangered Mexican fish. Biological Conservation 133(2): 169–177.doi:10.1016/j.biocon.2006.06.002 (HTML abstract)

  • Miller, Robert Rush & Fitzsimons, John Michael (1971): Ameca splendens, a New Genus and Species of Goodeid Fish from Western Mexico, with Remarks on the Classification of the Goodeidae.Copeia 1971(1): 1-13. doi:10.2307/1441593 (HTML abstract and first page image)

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