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In Parts 1 and 2, I discussed the inheritance of mutant
genes that affect the color of aquarium-bred angelfish. In this
article I shall add information on the location of these genes.
This additional knowledge is essential in order to know which
gene combinations are possible and also to enable you to predict
correctly the outcome of crosses involving more than one mutant
gene.
The angelfish's chromosomes (containing the genetic material)
are in pairs, one chromosome of each pair having come from each
parent. Each gene occurs at a specific location, called locus
(plural, loci), on the chromosome. Variations of a gene are
called alleles. Only one allele occurs at a locus; another
allele of that gene can occur at the same locus on another
chromosome.
Tests for Allelism
Black Angel (1 dose of dark and 1 dose of marble.)
Black Angel. (1 dose of dark and 1 dose of marble.)
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| Black Angel. (1 dose of dark and 1 dose of marble.) |
A marble female (having two doses of marble), mated to a
black lace male (one dose of dark), produced 23 marble and 22
black (one dose of marble and one dose of dark). This type of
black angelfish, called marble lace (Norton, 1971), has a
marbled pattern on the body that can be seen by shining a
flashlight on the fish. A true black (two doses of dark) has
faint vertical body stripes that can be seen by using a
flashlight.
When a wild-type (silver) female was mated to a marble lace
male, the offspring were 48 black lace and 46 marble. Since
there were no wild-type offspring, I concluded that the genes
for dark (D) and marble (Dm) act as alleles. In other words,
these genes are at the same locus.
A wild-type female and zebra lace male (one dose each of dark
and zebra) produced 9 wild-type, 6 black lace, 4 zebra, 5 zebra
lace. It is concluded that the genes for dark (D) and zebra (Sze)
are not alleles since the above cross produced some wild-type.
Black Angel. (1 dose of dark and 1 dose of new gold.)
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| Black Angel. (1 dose of dark and 1 dose of new gold.) |
A new gold female and true black male (D/D) produced 100%
black, which were not as deeply pigmented as the true black.
This type of black (one dose of new gold and one dose of dark)
has a slight bronze cast on the body and evident vertical bars.
Crossing two of these blacks resulted in an F2 consisting of 62
new gold and 200 black, no black lace or wild-type. Also a new
gold female and black male (whose parents were new gold and true
black) gave 214 black and 207 new gold offspring. Thus the gene
for dark (D) and new gold (dng) behave as alleles.
Black lace were obtained by mating true black and Hong Kong
gold. These black lace, which carried the recessive gene for
Hong Kong gold (see Part 2), produced an F2 of 29 wild-type, 49
black lace, 12 black, 4 Hong Kong gold. It is concluded that the
genes for dark (D) and Hong Kong gold (hg) are not alleles since
some wild-type offspring were produced.
Numerous blushing marble were obtained from a blushing
crossed with a fish that had one dose each of stripeless and
marble (having come from a blushing x marble cross). Since a
blushing marble would have to have one gene for marble and two
genes for stripeless, it is deduced that the genes for
stripeless (S) and marble (Dm) are not alleles.
A smokey female, crossed with a male having one dose of
marble, produced 79 wild-type, 157 marble, 86 smokey. Some of
the marbles were suspected of having one dose of smokey because
they exhibited one or more of these smokey features: (1) black
mouth, (2) black-tipped dorsal fin, (3) gray in the white
streaks in the outer part of the caudal fin. Two such males were
tested for smokey by mating them to wild-type females. This
produced: male #1: 126 wild-type, 269 marble, 123 smokey; male
#2: 27 wild-type, 47 marble, 21 smokey. Not only was smokey
present in the tested marble males but the genes for marble (Dm)
and smokey (Sm) did not act as alleles since the crosses
produced some wild-type offspring.
A male having one dose each of marble, zebra and smokey was
mated to a wild-type female, producing 37 wild-type, 136 marble
(including marble with zebra and/or smokey), 34 zebra, and 59
smokey (including zebra-smokey). Zebra-smokey looks like zebra
until the stripes disappear as the smokey pattern develops.
Since there were wild-type offspring, it is concluded that the
genes for marble (Dm) and zebra (Sze) are not alleles.
1 dose of marble and 1 dose of new gold.
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| 1 dose of marble and 1 dose of new gold. |
A marble female was mated to a new gold male, producing 241
wild-type and 217 marble. One of the marble F1 males, mated to a
new gold female, produced 105 marble and 111 new gold. Since no
wild-type offspring were produced, it is concluded that the
genes for marble (Dm) and new gold (dng) act as alleles.
Since (1) the genes for dark and marble behave as alleles,
and (2) the genes for dark and Hong Kong gold do not act as
alleles, it follows that the genes for marble (Dm) and Hong Kong
gold (hg) are not alleles.
A smokey male was tested and found to have one does of
stripeless since, when mated to a wild-type female, he produced
wild –type, smokey and stripeless offspring. Since there were
some wild-type offspring, it is concluded that the genes for
smokey (Sm) and stripeless (S) are not alleles.
1 dose of Zebra and 1 dose of stripeless.
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| 1 dose of Zebra and 1 dose of stripeless. |
A female with one dose of zebra, mated to a blushing male,
produced all stripeless offspring, some of which had more black
blotches on the body than I had ever seen on fish with one does
of stripeless but without zebra. When the ones with increased
splotching matured, their dorsal fins had an increased number of
light-colored horizontal bars (compared with wild-type), a zebra
characteristic. One of these that was suspected of having one
dose each of zebra and stripeless was tested by mating him to a
wild-type female. From the results, 188 stripeless and 220
zebra, it is concluded that the tested fish did have one dose
each of stripeless (S) and zebra (Sze) and that these genes
behave as alleles.
A blushing female, mated to a Hong Kong gold male, produced
100% stripeless, non-gold offspring. The F2 included some each
of blushing, Hong Kong gold blushing, stripeless, Hong Kong gold
and wild-type. It is concluded that the genes for stripeless (S)
and Hong Kong gold (hg) are not alleles, since wild-type
appeared in the F2 and since Hong Kong gold blushing would have
to have two doses of each of Hong Kong gold and stripeless.
Zebra lace. (1 dose of Zebra and 1 dose of dark.)
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| Naja gold beginning to lose the black pigment on its mouth. |
Since (1) stripeless and zebra act as alleles and (2)
stripeless and smokey are not alleles, then it follows that the
genes for smokey (Sm) and zebra (Zse) are not alleles.
A smokey female x new gold male produced smokey and wild-type
offspring. One of the F1 smokey males was mated to a new gold
female, giving 91 wild-type, 80 smokey, and 156 new gold. This
fits the expected ratio (1 wild-type: 1 smokey: 2 new gold), if
the smokey pattern is not expressed in a fish having two doses
of new gold. Therefore, half of the 156 new golds were assumed
to carry the gene for smokey. Further evidence that new gold, in
double dose, blocks development of the smokey pattern was
obtained by mating smokey parents, both of which came from
smokey female and new gold male. These produced 71 smokey, 33
chocolate (double dose smokey, see Part 1), 42 new gold, 32
wild-type. These numbers fit the expected ratio (6 smokey: 3
chocolate: 4 new gold: 3 wild-type), if the smokey pattern is
not expressed in the presence of double-dose new gold. Since
each of the spawns (from smokey male carrying new gold x new
gold female, and from smokey parents each having one dose of new
gold) produced some wild-type offspring, it is concluded that
the genes for smokey (Sm) and new gold (dng) are not alleles.
Since (1) zebra and stripeless behave as alleles and (2)
stripeless and Hong Kong gold are not alleles, is is deduced
that the genes for zebra (Sze) and Hong Kong gold (hg) are not
alleles.
It has already been stated that new gold in double dose
blocks expression of the smokey pattern. The same is true for
new gold zebra, which also has no black body pattern. A zebra
female that had one dose of new gold was mated to a new gold
male, producing 103 new gold (including new gold zebra), 57
zebra, and 73 wild-type. The genes for zebra (Sze) and new gold
(dng) are not alleles, since numerous wild-type were produced.
Although new gold zebra has no black pattern on the body and
fins, in juveniles it can be distinguished from new gold by its
three very faint vertical body stripes (paler than the rest of
the body) instead of two pale stripes in new gold without zebra.
An adult gold zebra has approximately 12 light-colored
horizontal bands in the dorsal fin, while a new gold has about 7
or 8.
Since (1) new gold behaves as an allele of dark and (2) Hong
Kong gold is not an allele of dark, it follows that the genes
for Hong Kong gold (hg) and new gold (dng) are not alleles.
Summary of the Genes
All of the major color patterns in today’s aquarium-bred
angelfish are due to seven mutant genes if we eliminate from
discussion the Naja gold, which is no longer of commercial
importance and is difficult, if not impossible, to locate. These
seven genes occur at four loci, as follows:
Locus #1: Hong Kong gold (hg), recessive to wild-type
Locus #2: smokey (Sm), dominant to wild-type
Locus #3: stripeless (S), dominant to wild-type; zebra (Sze)
dominant to wild-type
Locus #4: dark (D), dominant to wild-type; Marble (Dm), dominant
to wild-type; new gold (dng), recessive to wild-type
Practical Applications
Since in most cases in angelfish has only two doses of a set of
alleles, certain limitation exist in gene combination. For
example, there is no advantage in trying to get an angelfish
with one dose of marble and two doses of new gold, since and
individual has only two doses, not three, of this set of
alleles. The possible combinations of the multiple alleles dark,
marble and new gold are:
(1) one dose of dark
(2) one dose of marble
(3) one dose of new gold
(4) two doses of dark
(5) two doses of marble
(6) two doses of new gold
(7) one dose of dark and one dose of marble
(8) one dose of dark and one dose of new gold
(9) one dose of marble and one dose of new gold
The gene for new gold, in double dose, blocks expression of
smokey and zebra. In contrast, one dose of new gold enhances the
expression of both dark and marble, resulting in an increased
black pigmentation.
There are three genotypes of marble angelfish:
(1) two doses of marble (Dm/Dm)
(2) one dose of marble (Dm/d+)
(3) one dose of marble and and one dose of new gold (Dm/dng).
As was discussed earlier (Part 1), the double-dose marble breeds
true but is slow growing and less vigorous than the single-dose
marble. I also explained in that article how to obtain spawns of
100% single-dose marble, by crossing wild-type with double-dose
marble
An angelfish with one dose of marble and one dose of new
gold, which also is a good commercial type (perhaps better than
single-dose marble because of it jet black markings), is also
vigorous. Because of individual variation, double-dose marble
may be difficult to distinguish from the marble-new gold type.
However, if you can observe an entire spawn of only one type you
can tell them apart because most double-dose marbles are mostly
black and have very little white area (the dark areas are jet
black as in the marble-new gold type). In comparison, most fish
with one dose each of marble and new gold have larger white
areas. The dark pattern of a single dose marble is a mixture of
black and gray, not as striking as the pattern of the marble-new
gold type.
To raise 100% marbles of either single-dose marble or the
marble-new gold type, you need a double-dose marble for one
parent. See Part 1 for instructions to obtain double-dose
marble. The two crosses to obtain 100% of the best commercial
marbles are:
(1) double-dose marble x wild-type (silver): 100% single-dose
marbles
(2) double-dose marble x new gold: 100% marbles with jet black
pattern
The true black (double-dose dark) angelfish breeds true but
is slow-growing and unsatisfactory for commercial production. A
fish that is just as black but that is much more vigorous is the
one that has one dose of dark and one dose of marble (D/Dm). To
get 100% of this type of black, which has a faint marbled body
pattern under strong light, cross a double-dose marble female
with a true black male.
Another satisfactory black, as far as vigor is concerned, is
that one that has one dose of dark and one dose of new gold (D/dng).
The body of this fish is somewhat brassy and the body stripes
are more obvious than in a true black. To get 100% of this type,
cross a new gold female with a true black male.
An aquarist is likely to buy whatever type of black angelfish
is available, which today in most cases will be either marble
lace (D/Dm), or dark-new gold (D/dng), and raise them for
breeders. Using marble lace parents, you will get about 75%
black (including 25% true black and 50% marble lace), and about
25% double-dose marble. If dark-new gold parents are used, you
will get about 75% black (including 25% true black and 50%
dark-new gold), and about 25% new gold. There are disadvantages
in using these crosses to obtain black angelfish. (1) You will
not get 100% blacks and you will need to sort. (2) The true
blacks will grow more slowly than the other blacks and will
reach selling age later. If you happen to buy black angelfish
that are different genetically but not true black, you could own
breeders in which one is the dark-marble type and the other is
the dark-new gold type. If these types are crossed, they would
produce 25% true black, 25% black (dark-new gold), 25% black
(marble lace), and 25% marble. This spawn also would require
sorting.
As was discussed in Part 1, crossing a true black with a
wild-type (silver), produces 100% black lace offspring. You will
not get this result if the black parent is not true black (two
doses of dark). Crossing a wild-type with a black that has one
dose each of dark and marble will produce 50% black lace and 50%
marble. Or, if you cross wild-type with a black that has one
dose each of dark and new gold, you will get 50% black lace and
50% wild-type.
A blushing angelfish (two doses of stripeless) has very
little black pattern on the body. Yet, the marble pattern
develops when present with blushing, so a blushing marble
angelfish (having the marble pattern along with red gill areas
in juveniles), is possible (Norton, 1971). Knowing that the
genes for stripeless and zebra act as alleles, you can save
yourself the trouble of trying to get a blushing zebra
angelfish. The possible combinations of these two genes are:
(1) one dose of stripeless
(2) two doses of stripeless
(3) one dose of zebra
(4) two doses of zebra
(5) one dose of stripeless and one dose of zebra
Number 5 above differs from number 1 by having more black
markings, and also more green body color in the adult.
Genotypes
The genotypes listed below are for the angelfish discussed to
date:
Hong Kong gold = hg/hg
Smokey = Sm/+
Chocolate = Sm/Sm
Stripeless (Ghost) = S/+
Blushing = S/S
Zebra = Sze/+ or Sze/Sze
Zebra, one dose stripeless = Sze/S
True black = D/D
Black lace = D/+
New gold-dark = (black) (D/dng)
Light marble = Dm/+
Dark marble = Dm/Dm
Marble with jet black pattern = Dm/dng)
New gold = dng/dng
Zebra lace = Sze/+ D/+
Literature Cited
Norton, Joanne, Angelfish – breeding and genetics.
The Aquarium 6 (No. 10) 34-41. 1971
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