tazdevil":1sfwd2se said:
Pardon my stupidity, but whats wrong with crossbreeding killifish?
To answer that I've got to give a little background on killifish. Killifish, at least those obtained from reputable sources, are identified by species and then by collection code. A few are further identified by collection year after the collection code, if multiple collecting trips were made to the same locale. For example: Nothobranchius rachovi Beira 98, which designates n. rachovi collected in an area identified as Beira back in 1998.
The reason why this matters is because of the genetic diversity within the same species between one collection locale and another. Aphyosemion bivitatum Funge is quite different, visually, from a. biv Volcanum or a. biv Tiko. The reason for the large number of different strains of the same species has to do with these fish rapid turnover of generations and the complete isolatedness of one breeding population to the next, even if only a few hundred feet seperates them. Crossbreeding different strains of the same species muddies the strains and loses what makes each unique. Add in to that the annual nature of many of these fish, and their unusual housing, breeding and rearing requirements, and you end up with lines that are only maintained in captivity by diligent effort on the part of hobbyists. Should crossbred progeny ever end up in a main breeding line, the entire captive strain could become contaminated.
And this is easier to happen then you might think. Crossbred males are usually very easy to spot, since the males are so colorful and distinct to begin with. But with the females it can be totally impossible to tell visually. My aphyosemion australe female looks like a particularly ugly beige female guppy. My two notho females, of different species let alone strains, look exactly alike; two vaguely pupfish looking fish, light lilac in color.
It gets worse when you start talking about crossing two different species. Within the same family (and within certainly closely related families) this is easy to accomplish. Males and females of different species will readily breed and produce offspring. Most of the males produced will be sterile, and in succeeding generations the sterility only becomes more endemic until none of the males descended from such a cross can breed. While it's possible to get some truly stunning looking fish this way, they simply can't be maintained. With the amount of effort it takes to maintain lines in the first place, especially where annuals are concerned (some of the extremes include eggs that can take as much as nine months to be ready to hatch, in a fish whose lifespan won't even reach nine months long), it's kind of wasted effort. And even worse, if the fish get disseminated to other aquarists they're stuck with fish that are sterile (or who's offspring will be).
Killies are more at risk for habitat destruction than most other organisms, if only because a certain 5' pond may be the only place where a particular strain of a particular species is found. Many strains present in the hobby may no longer exist in the wild for this reason.