A Swordtail Breeding Program
by Barry Lynch
from Wet Pet Gazette, Norwalk Aquarium Society
Aquarticles
In January of 2002, I acquired an adult pair of "saddleback" albino
swordtails (Xiphophorus helleri). In addition to the red eyes that come with all
albinos, the saddleback has a soft golden white body highlighted by an orange dorsal fin
and some orange in the surrounding area. The male is further accentuated by a long
iridescent green swordtail. In March, the female gave birth to numerous fry. By June, 160
mature adults were occupying my 75 gallon tank.
Hi-Fin Breeding Program: Although I consider the saddleback albino to
be extremely attractive, I wanted to do more than simply reproduce it. I mentioned this
interest to Joe Mulvy at the House of Fins. He suggested I introduce a high dorsal fin to
the albinos. As it turns out, he had that day received a male "red tuxedo"
swordtail with a beautiful high fin. (The fish came from a local elementary school closing
for the summer - you never know where you'll find the right specimen!) So, I left the
store with a great fish and embarked upon a breeding program I never imagined would last
at least two years.
Not having a separate tank then available, I introduced the male to my 40 gallon
community tank and added two albino females. Keeping in mind (i) the females might already
have been impregnated by their siblings and (ii) the ability of female swordtails to store
sperm, I resolved to wait two months before insolating the females for birthing.
False Start - Albinos: In late August, I observed that both females
were quite pregnant and moved one to a 10 gallon birthing tank. Shortly thereafter, there
were many fry in the tank - all albinos. Since the albino gene is double recessive, none
of the progeny of the red tuxedo and the albino should have been albino (except in the
extremely unlikely event the red tuxedo possessed an albino gene). Clearly, these fry came
from a previous pairing the albino female had had with an albino male. My frustration
increased when I shortly thereafter discovered four baby swordtails (3 reds and 1 tuxedo)
in the community tank. I obviously had moved the wrong female to the birthing tank!
First Generation - Reds & Tri-Color Tuxedos: I kept the correct
female with the tuxedo male in the community tank for about three weeks and then moved her
to the 10 gallon birthing tank. Two days later my patience was rewarded by approximately
60 fry - divided evenly between reds and tuxedos. The reds (more orange/red than the deep
red of the red velvet swordtail) proved to be nice fish. The tuxedos (gold in the upper
front part of the body, red in the upper back and the entire lower part of the body and
black running the length of the body in the middle) proved to be striking fish.
More importantly to my program, since the mother was albino, each of the fry possessed
an albino gene. Now, the question was whether high dorsal fins would appear. In about a
month, it was clear that at least some of them would be hi-fins. As it turns out, about
25% (all of them males) were hi-fins.
Separation by Sex: To prevent unwanted pairings as the fry grew, I
endeavored to separate the fish by sex as their sexuality became evident. This proved to
be a little more challenging than one might expect. Male helleri swordtails
generally develop in two morphological groups. The first group emerges early, tends to
have narrow bodies and long swordtails and, in the case of hi-fins, thin hi-fins. After
you have removed the first morphs, you think you have successfully segregated the sexes.
However, several weeks later, some of the "females" start showing their true
male sexuality. These are the second morphs. They are thicker than the first morphs, grow
considerably larger and, in the case of hi-fins, the hi-fins are the more desirable wide
and flowing fins.
Second Generation - Albinos: In December, I isolated a red hi-fin male
with a tuxedo female. Genetic theory would tell you that, since each possessed one albino
gene, approximately 25% of the resulting brood would be albino. Not surprisingly, the
theory proved correct. Out of a rather large brood of 150 fry born in February, 36 were
albinos. (The remainder consisted of reds, red tuxedos, tri-color tuxedos and
"pineapple" swordtails - none germane to this article.) Initially, all of the
albino fry appeared to be saddlebacks. Within two days, however, 12 distinguished
themselves by showing a golden orange hue. In about a month, all 12 had turned solid red
in color and maintained this coloration through early adulthood. (Undoubtedly, this is due
to a lineage consisting of a red father and a red tuxedo grandfather.) In any event, I
started entertaining visions of not only developing hi-fin saddlebacks but also hi-fin
"red-eyed reds". What I didn't know at the time was that my "reds"
were due for another color change.
Segregation by Color: Determined to develop both lines, I segregated
the albino fry by color. As the fish matured, it became clear I enjoyed some good fortune.
Even though the percentage of hi-fins remained rather low (about 25%), both color groups
contained hi-fins and some females were showing hi-fin signs (but not true hi-fins).
Third Generation (Saddleback Group): In late May, I isolated two young
saddleback albinos (a first morph hi-fin male and a "semi" hi-fin female) in a
10 gallon tank. In early July (having first removed the male), the female gave birth to 30
saddleback fry. The small brood is due to the youth of the mother. Hi-fins are just
starting to develop in this group of young swordtails.
Third Generation (Red Group): In June, I similarly isolated two red
albinos. I was curious about whether or not the red coloration would be passed on to
succeeding generations. In late July, the female produced 38 fry. Unlike their parents,
about 50% possessed the golden orange hue at birth. Like their parents, the remainder
developed the golden orange hue within several days. All are now in the process of turning
red. In short, it is quite clear the coloration is being passed on. As discussed below,
what is not clear is what the final coloration will be.
Color Changes: I suppose I should note that the fish I have described
as saddlebacks have remained saddlebacks and are producing saddlebacks - e. g. there are
no color changes in these fish. The color changes are limited to the so-called
"red" group and its progeny. I have already described how the color changed from
soft white to golden orange to red. It hasn't stopped. In the mature adults, the red has
disappeared from the lower part of the body and been replaced by a silvery green sheen. I
am not convinced the color change has been completed.
Continuing Goals. My initial objective was to introduce the hi-fin to
the saddleback albino swordtail. In this regard, I have succeeded. The breeding program
has, however, generated additional goals which I continue to pursue. These include the
following:
Hi-Fin Females: No hi-fin females were produced in the first
generation. In the second generation, a few females with semi hi-fins (the dorsal fin
being about one third the size of that in the hi-fin male) emerged. The third generation
albinos (both lines) have a hi-fin father and a semi hi-fin mother. Hopefully, this will
produce true hi-fin females. The third generation young will have to mature several months
before this question is answered.
Hi-Fin Percentage: To date, only about 25% of each brood have been
hi-fins. I would like to significantly increase this percentage. This may not be possible.
Two friends I consider to be authorities have differing views. One believes the hi-fin
trait is only semi-dominant and accordingly that the percentage will remain low. The other
believes the trait to be dominant and that, when I succeed in developing hi-fin females to
mate with the hi-fin males, the percentage will greatly increase. Time will tell.
Hi-Fin Red-Eyed Reds: At one point in time, I thought the development
of hi-fin red-eyed reds would be one natural result of the breeding program. That was
before the "reds" started their next color change. What I didn't mention above
is that one adult male has, however, stubbornly retained all his red color. He was always
the deepest red of the bunch; but, since he is not a hi-fin, he has not been used as a
breeder. I may eventually use him to try to establish color unless a male with his
coloration and a hi-fin emerges from the July red group. Alternatively, I may approach one
of you currently maintaining red-eyed reds for assistance.
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