Shanon asked in PetsFish · 8 years ago

Killifish cross-breeding? Is it possible?

Can I cross-breed Nothbranchius Guentheri with Nothobranchius Rachovii Beira 89? Will The frys be healthy if I do so? Are there any successful cases?

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  • 8 years ago
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    A very interesting & sophisticated question! It could stir up quite a bit of discussion & controversy at a meeting of killifish keepers or on on-line forums.

    One can sometimes breed a male or female of one species of killifish to another and get fertile eggs. Fertilization may be difficult or impossible. A very few eggs will hatch. Most eggs will not be fertilized or the embryos die of something, often of a cancer. The fry may die "mysteriously." But rarely they will develop, hatch, grow and even show adult colors. Most adults will be sterile mules.

    I inadvertently crossed plant spawning killies because we bought a pair of what today would be called Fundulopanchax walkeri, with a beautiful orange male & a typically nondescript female. They were spawned (as 70% of the 1,000+ killies can be) in an acrylic mop. 100s of eggs were collected. None hatched in water incubation. Put on wet peat moss & then in water two of a batch hatched. When the "male" of the two grew up it was larger than walkeri and a dead ringer for a cross pictured in Scheel's books and captioned as a gardneri x walkeri cross. Put together the male fatally mauled the female (who may have had no eggs to lay) & after a couple of years he died without descendants.

    Clearly someone got sloppy & let a gardneri female jump into a walkeri tank. Lesson learned - tightly cover tanks. Also don't put similar species even on the same aquarium rack.

    Nothobranchius, as you know, are annual killifish, lay eggs in the clay rich mud. In the dry season the eggs survive in the mud while the parents have perished.

    Different wet-dry seasons and rain patterns mean that Nothos in different areas will have different "dry periods." N. guentheri from the Zanzibar area is considered one of the easiest to keep, breed, store the eggs of and hatch. Incubated at roughly 75 degrees F/ 24 C is 2-3 months. (Star wetting them a 2 months. One can dry & wet the peat again & again.)

    Much further south, in Mozambique and South Africa. lives N. rachovii. Your stunning strain is one of those more often kept by "killinuts." The dry season is longer there. A recommended incubation time for them at 75 F/ 24 C is 5-7 months.

    That of course doesn't take into consideration the humidity of the peat moss. Possibly there are also other variables in incubation & hatching and that is why velvet prone Nothos are more challenging to keep & reproduce than many other killifish.

    The probable difference in genetics, the distance between where the two species are found and the incubation periods suggests to this ordinary aquarist that the odds are against a successful cross between N. guentheri & N. rachovii.

    Another reason to be careful about crossing killies is that they are only modestly common to rare in the hobby. If we cross them and don't reproduce the species often enough, they may be lost to the hobby. Because of changing political conditions. changing climates & habitat alteration, some killie strains will never be found again in the wild.

    Sometimes newly discovered strains of killifish are described & fish from several collecting locations are labeled as a certain species. But there are differences between their colors & form. Later it was discovered that there were 2 fish previously considered somewhat unique color forms of N. rachovii are now considered additional species. One of the different looking strains of N. rubripinnis is now known as N. cardinalis. If we had crossed these strains, the original may be lost to the hobby. In even if the first generation cross is viable. colors fad with the generations, as may fertility.

    In one rare case the late Bob Skirm crossed N. guentheri with the neighboring N. kortausae. The first generation was a very attractive combination of both male's colors. He succeeded in getting a couple succeeding generations. However the male coloration became very nondescript. Male killifish (among other species) attract females and often need the correct bright colors and appropriate pre-spawning display to attract females to them. (The good dancers often get the girls.) If the males get too plain, they may be out of luck unless they can force females to approach a spawning spot. Or the strain ends.

    If you just got pairs of these species, why not hone your ability to breed & raise them? Talk to other Notho keepers. Then decide if you wish to cross extra pairs of them in controlled, separate quarters, just to see if they cross. :)

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  • 4 years ago

    Killifish

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