Akvárium, založeno r. 1899 Late First Club of the Aqua and Terra Friends in Czech Kingdom from Prague
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The livebearer with ungrateful  character  Click for film (1,94 MB)

RNDr. Roman Slaboch

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Knife livebearer (Alfaro cultratus /Regan, 1908/) comes from Central America (from the south of Nicaragua to the north of Panama). It is attractively shaped fish with a couple of unpleasant features. One of them is the indisposition to take the feed from the bottom. It is not so big problem; keep them with another species that cleans the bottom, and the problem is managed. It can be even any peaceful species of livebearers, because scharp-belly livebearer interbreeds only inside of its species. The reason is quite complicated precopulation observance of the male, which swims just above the female’s head and touches her crown with gonopodium. In the next stadium, male beats with quick motions of gonopodium on her head. If female doesn’t want to escape, he goes down, floats beside her, and tries to inseminate her. It is obvious, that this behavior formula can’t any other species comply.

Other inconveniences of the breed are their jumping performances. Above all, maturing males (4-5 months) jump often in chases. The biggest losses are consequently from this period, and it is the case of the majority of females in aquarium breeds.

Last but not least, they have unpleasantly high reception of increased quantity of nitrogen fusions in the water. Concentration, which other species’ behavior doesn’t indicate, results in the preterm litters of the immature young. The breeder recognizes it after as much as the female doesn’t bear. Generally, after this time the concentration more increases, fish have enlarged orbs, stop to take the feed and die. Periodic exchange of water is consequently vital condition.

Many a literature features the taste for running water. But in my breeds fish avoid the outlet of the filter. Also the observations from the nature don’t support this statement directly. But it’s true, that adult big ones stay in the middle of the strain (if there is any) and it is good chance to fish them, because it’s simple to take them with fyke. Literature and observation in the natural habitats and in the breeds come to a verdict that A. cultratus needs bushy planted tank. In the nature it’s made up with the thicket of roots and fallen branches for the most part, but the effect of perfect refuge is the same. Hiding places need first the freshly born young (8 mm), which tempt the attention of adults with their jerking motions, and great deal of the young enrich their feed. In the nature I saw the smallest young almost entirely in the shallow places with 0,5-1 cm of water. In 24°C, the gravidity lasts approximately 24 days and it’s lowly perceptible.

They mature after 6 months. Females grow up to even 8 cm, males maximum 6 cm. On the basic ochre color is beautiful metallic blue glaze, which excels only at the exposure of sunshine. Czech specific epithet scharp-belly was assigned because of keel ordering of the scales on belly.
The fish also “enjoyed” scientific descriptions:

  1. Alfaro cultratus Regan, 1908;

  2. Petalosoma cultratus Regan, 1908;

  3. Petalurichthys cultratus Regan, 1912;

  4. Alfaro acutiventralis Meek, 1912;

  5. Petalosoma amazonum Regan, 1911;

  6. Petalurichthys amazonum Regan, 1912;

  7. Alfaro amazonum Regan, 1913;

Mr. Regan was evidently at loose ends.

Due to unusual character of the shape, Alfaro cultratus is one of the few wild livebearers, which are available in akvashops.



Wischnath, L.,(1993): Atlas of Livebearers of The World, T.F.H. Publications, Inc.; USA, 336 ss.


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