NEWS103
24
ust like the majority of other colors
and patterns, the white body color
made its way into the swordtail
(
Xiphophorus hellerii
) via the Platy
(
Xiphophorusmaculatus
). Even in the wild
thePlatyoccurs in a very largenumber of
geographical races (subspecies), which,
however, have yet to be given scientific
names. These races differ fairly noticeably
from one another externally by their
coloration and patterning. Initially it was
established that itwaspossible toproduce
newcolorcombinationsvia thecrossingof
these races in the aquarium. The
mechanisms that form the basis of this
J
The pure white ‘Ghost’ Platy is the starting
point for all cultivated Swordtail formswith a
whitebase color.
The ‘Marlboro’Swordtail, the latest cultivated formof
Xiphophorushellerii
. All Photos:FrankSchäfer
The tricolor Swordtail appeared in the late 1990s. It was the first Swordtail
with a purewhite base color to becomewidely established in the hobby.
Nowadaysweknow several cultivated forms inwhich thebodybasecolor is
white,and someof them firstappearedon themarket justa fewweeksago.
Newcultivated forms
of Swordtail
byChristianPlaul
color
inheritance
have
fascinated
geneticists right from thestart.Later itwas
discovered that crosses between Platies
andSwordtails are fertile.
ThecrossingofPlatyandSwordtail
This isn’t in fact quite as easy as stated in
manybooks,but is essentially feasible.The
offspring
of
these
crosses
are
intermediates, that is, they exhibit
characters midway between Platy and
Swordtail.Thesehybridscan thenbeback-
crossed with the Swordtail, producing
fishes that resemble the Swordtail in form
but alsocarry thecolor genesof thePlaty.
A luckyaccident formedicine
Someof these Swordtail crosses developed
an inheritable formofcolor-relatedcancer in
the formof tumors consistingof collections
of black pigment cells on the caudal
peduncle. This was the first type of cancer
known to science that could be produced
deliberatelybybreeding.A lotof information
on cancer was obtained by studying this
form, so ultimately the aquarium hobby
saved the livesofmillionsofpeople.
LebendgebärendeZahnkarpfen
