|
Table
4. Phenotypes of Angelfish not Explained by Mendelian Genetics
|
|
Phenotype
|
Discussion
|
|
Orange
Pigmentation
|
Orange
pigmentation appears in many varieties of angelfish including silver
angels (+/+). However, it shows up best in white areas of Koi angels
(gM/gM S/S or gM/g S/S) and White Blushing Angels (g/g S/S) . Orange
pigmentation is naturally concentrated in the crown area (dorsal area
of body between the mouth and the base of the dorsal fin) but can also
occur on any body part. This characteristic does not appear to behave
according to Mendelian rules and is probably controlled by many genes.
The genes appear to be "fluid" like the marble (M) gene. The propensity
of the orange characteristic to be enhanced is similar to the enhancement
propensity of black marbling in marble, koi, and gold marble angelfish.
In these 3 varieties, black marbling can be selected to produce fish
that are almost all black. Likewise, in Koi, orange can be selected
to produce fish that are all orange. It seems that the expression of
orange may be genetically related to marbling based on our experience
of enhancing orange by out breeding to marble angels and then doing
F1 crosses. Another observation suggesting a relationship between black
marbling and orange is the observation that a pair of Koi which are
over 85% orange with very little marbling can produce fish with extensive
marbling. The orange pigmentation of koi seems to be linked somehow
to the gold marble gene because out breeding to pure white blushers
with no orange (g/g S/S), followed by an F1 cross, does not produce
orange pigmentation in any of the F2 white blushers. Therefore, the
mechanism by which out breeding to marble angelfish enhances coverage
with orange may involve other mechanisms such as gene modification.
It is true that orange pigmentation can be selected in white blushers;
however, the results of this have not produced fish as orange as orange
koi. One form of orange pigmentation in white blushing angels is the
orange crowned white blusher which has a distinct orange crown. We have
also produced white blushers in which the orange crown was transferred
to the ventral area as orange streaks extending into the anal fin. Several
times, fish were produced in our hatchery with an orange patch which
we believe may have been the result of "crossing over" from
the chromosome carrying the gM gene in orange koi angels to the g gene.
|
|
Stripe
pattern in gold marble angelfish
|
The
presence of one or more apparent black stripes or partial stripes in
gold marble and koi angels suggests that an interaction between the
M of gM and the wildtype stripe (+) may exist. However, breeding fish
with this characteristic does not appear to increase the strength of
the phenotype or the frequency of its occurrence in the offspring. In
fact, our experience breeding gold marble angelfish with "marble stripes"
resulted in broods with no occurrence of the characteristic.
|
|
Swallowtail
|
This
characteristic is a partially split anal fin which shows up sporadically
in many angelfish hatcheries including ours. We have produced viable
offspring when breeding 2 fish with the swallowtail characteristic,
but none of the offspring were swallowtails. I have heard that some
normal finned parents throw a few Swallowtails in every brood. If this
is true, it suggests that the swallowtail characteristic has a genetic
basis and is not just a developmental abnormality. If this is true,
it suggests that this characteristic might be transmittable but apparently
not according to Mendel's Law. Perhaps if a discreet Mendelian gene
for swallowtail exists, it is a gene for "potential expression" dependent
on certain environmental conditions?
|
|
Fantail
|
Like
in goldfish, a fantail angelfish has a split or double caudal fin. Only
one has shown up in our hatchery. To our knowledge this has never been
seen before.
|
|
Blue
coloration
|
Many
breeders are trying to select for blue pigmentation which is observed
as iridescence in the fins and scales of almost all angelfish varieties.
It can also be observed as a blue hue in the flesh of blushing angels.
Some wildcaught angelfish have spectacular blue irridescent mottling
reminiscent of discus. The varieties most commonly chosen for blue selection
appear to be blushing, smokey blushing and chocolate blushing. Blue
coloration is also prominent in varieties carrying zebra genes and in
silvers. At present, we don't know if blue coloration can be enhanced
by supplementation with a nutrient like carotenoids in orange angelfish.
The blue comes in many shades: indigo, greenish blue, sky blue….
An all blue angelfish of discus quality has yet to be developed.
|
|
click below to go back to:
|
|
