Aside from all the negative
press associated with the word. aquarists may not know the benefits of selective
inbreeding, I went through some genetics books to gat a working definition of
the term. They define inbreeding as the mating of related individuals. The
different genes at a common locus on a chromosome are called alleles. If a fish
has two identical aIleles it is a homozygote. Related fish share alleles through
one or more common ancestors. I suppose you could get homozygous fish from
unrelated fish, but inbreeding greatly increases the chance of this happening.
In and of itself inbreeding is neither good or bad. It can be abused and it can
certainly be used constructively
Most of us are aware that
domesticated swords and platies were produced by hybridization. In these
breeding schemes hybridization is almost always followed by inbreeding. In the
second step the hybrids are often bred brother to sister or back to one of the
parents. The only exception to this is when the hybrids are sterile. For
instance, the only way to get mules is to mate horses with donkeys.
As hobbyists we can make use
of a type of inbreeding called Linabreeding. I use this technique whenever I
come across an outstanding male swordtail. First, bread this male to a virgin
female to be assured he is the father of the resulting fry. Than bread this male
back to his descendants - in other words back to his daughters and
grand-daughters. This is done because the animal you’ve chosen is so
outstanding you want his descendants to resemble him closely. This is how you
create a strain of outstanding males as opposed to random mating where a good
fish pops up every now and then. Every time you breed your best male back to his
descendants you are increasing his contribution to the gene pool. Livestock and
fish hatchery managers often go this route.
Our goal should be to produce
show quality strains. not just show quality individuals.. Someday I would like
to sec a show where entrants are required to bring in a dozen of their best fish.
A species maintenance approach to domesticated livebearers would tie in nicaly
with this goal.
Reproduced from the ALA Magazine Livebearers Issue 98 March/April 1988