Page 73 - Encyclopedia of Aquarium and Pond Fish, 3rd Edition

FISH GENETICS 71

Selective breeding The Parrot Cichlid,
When a mutation that confers a desirable developed in the late 20th
modification—like a color change—occurs, century in Asia, is perhaps
the most controversial
it must be established in future generations example of hybridization.
by a careful breeding program. This not only Its ancestry includes
retains the favored characteristic but also Firemouth and Midas
ensures that the new variety does not carry Cichlids (see p.136).
any genetic problems. A common way to do
this is outcrossing, which involves pairing the
fish with an unrelated individual of the same
species that displays normal coloring and
patterning. The resulting offspring will be
normal in color, but they will carry the
mutation for the color change. After further
pairings with the progeny of similar matings,
a number of the new-colored fish will be present
among the offspring. These can be separated out
and allowed to mate with each other. Such a breeding
program improves the genetic base, ensuring that the
resulting individuals are less closely related. Mating together
two fish from the same brood—or inbreeding—can result in
offspring that produce reduced numbers of fry or are infertile,
especially when this is carried out over several generations.
Hybridization
Under normal circumstances, members of a single species
breed only with other individuals from that species. It is
sometimes possible, however, to persuade individuals from Once a successful
two different species to pair, creating offspring with novel variety, such as this Black
characteristics. This method for creating new aquarium Variegated Delta Guppy
(Poecilia reticulata), has
varieties is controversial, because these fish would never exist been established, the best
in the wild. Hybridization has been used very widely to create parents are chosen for
variant forms of the popular livebearers, including the well- each future pairing
known Black Molly (see p.168), strains of the more colorful to ensure that the
strain is maintained
gouramis, and the spectacular Parrot Cichlid (see above). and improved.

Brown-Red Alancea Discus Red-Spotted Turquoise Discus Turquoise Discus
Extensive turquoise-
Streaks and spots blue coloration over
over the body the whole body

Pure blue
markings

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