Dark Locus:
Black Phenotypes
The allele that is responsible for the black coloration in black
phenotypes is referred to as the “dark” allele and is designated with
the symbol D.
Possible black phenotypes are:
Double Dark Black (D/D)
Hybrid Black (D/g, D/Gm, D/M)
Black Lace (D/+)

Black
(D) exhibits co-dominance with the wild type allele (+). It is
dominant to marble (M), gold marble (Gm), and gold (g) alleles.
Three
distinct phenotypes of black occur: black, hybrid black and black
lace. Black angelfish are homozygous for the dark allele (D/D) and
are commonly called “double dark” blacks. Hybrid blacks have one
allele for dark and one for marble, gold marble or gold. Black lace
angelfish contain one dark allele and one wild-type allele. The table
below summarizes how the allele for dark interacts with other alleles
at this locus to form the black phenotypes.
BLACK PHENOTYPES |
Phenotype: |
Double Dark
Black |
Hybrid Black |
Black Lace |
Genotype: |
D/D |
D/M, D/Gm, or
D/g |
D/+ |
Pattern of inheritance: |
|
Dark is
dominant to Marble, Gold Marble, and Gold |
Dark is
co-dominant with wild type (blending of traits) |
Factors that Affect Expression of the Black Phenotype
The dark allele is constant in its expression, meaning that if it is
present in the genotype, it will always express in the phenotype
(except in an albino).
Changes in the Phenotype as the Angelfish Matures
In both double dark blacks and hybrid blacks, the black coloration
is initially a light gray in the fry and young juveniles, allowing
underlying striping to show through clearly. The dark color deepens
as they mature, masking the stripes under normal lighting.
Double
Dark Black
A double dark black is homozygous for the dark allele, with the
genotype D/D. A good quality double dark black will be nearly carbon
black, and stripes will not be visible. However, if a photo is taken
with a flash, or if a flashlight is shined directly at the fish,
underlying stripes can be seen. As it matures, it often develops a
blue hue in the gill area.

This photo of a
double dark black was taken with a flash, which reveals the underlying
stripes.





A double dark black generally grows more slowly than a hybrid black
or a black lace, although more vigorous strains are being raised today
as a result of good breeding programs.
Hybrid Black
Hybrid black angelfish have one dark allele paired with a marble
(D/M), gold marble (D/Gm), or gold allele (D/g). The most
popular choice for a hybrid black is to pair the dark allele with
gold. This results in a deep creamy black color.
With
hybrid black angelfish, an underlying pattern can be seen under a
bright light or in a photograph taken with a flash. The genotype D/g
will have underlying darker stripes, whereas the genotypes D/M and
D/Gm will have underlying darker marbling.
A hybrid black will generally grow faster than a double dark black.
A good quality hybrid black will be nearly as dark as a double dark.


Black
Lace
The black lace is an attractive phenotype that is formed by
combining one dark allele with one wild allele: D/+. The dark and
wild alleles are co-dominant, resulting in a blending of the two
traits. This results in coloration in which the body is somewhat
darkened to a light charcoal color, but not a deep black. The wild
type stripes show clearly. The tail and fins have a lacy pattern.
The stripes will fade or darken with the mood of a black lace, as in a
silver angelfish. The overall charcoal coloration of the body,
however, will remain constant.

Photo: Black Lace – The body is darker than the wild type silver
angelfish, but lighter than a black angelfish. The black stripes of
the wild type are clearly seen. The tail and fins have a lace
pattern.




Gene
Interactions
Many popular and attractive phenotypes are formed when black
phenotypes are combined with non-wild alleles for other genes.
Interactions with the Zebra/Stripeless Locus
The table below shows phenotypes that result when black phenotypes
are combined with alleles at the zebra/stripeless locus. A zebra
lace, for example, results when one or two zebra alleles are added to
the genotype for a black lace.
Interactions with the Smokey Locus
This next table shows phenotypes that result when black phenotypes
are combined with alleles from the smokey locus.
Phenotypes resulting from Black + Smokey (Sm) |
Alleles |
D/+ |
D/D |
D/M, D/Gm, D/g |
Sm/+ |
Smokey Lace
 |
Smokey Black |
Smokey Hybrid Black |
Sm/Sm |
Chocolate Lace |
Chocolate Black |
Chocolate Hybrid Black |
Interactions with the Albino Locus or Halfblack Locus
The albino trait is recessive, so it will only express when present
in the homozygous form (a/a). Albino will suppress the development of
dark pigment, resulting in an albino angelfish.
Halfblack is also a recessive trait that will only express when
present in homozygous form (h/h). The halfblack trait will be visible
when added to the black lace phenotype. However the black and hybrid
black phenotypes are already black colored, so even if the halfblack
trait expresses, it won’t be discernable against the black pigment
from the dark allele.
Phenotypes resulting from Black + Albino (a)
or Halfblack (h) |
Alleles |
D/+ |
D/D |
D/M, D/Gm, D/g |
a/a |
Albino Black Lace |
Albino Black |
Albino Hybrid Black |
h/h |
Black Lace Halfblack |
Black Halfblack |
Hybrid Black Halfblack |
Interactions with the Streaked Locus, Pearlscale Locus, or Veil Locus
When alleles from the streaked locus, pearlscale locus, or veil
locus are added to a black phenotype the color the black phenotype is
not altered. Instead, the non-wild alleles at each of these loci adds
an additional effect.
The streaked allele is dominant, so one or two streaked alleles
(St/+ or St/St) will result in addition of a white stripe to the body,
dorsal fin and anal fin.
Pearlscale is a recessive trait, so will only express when present in
the homozygous form (p/p). Even in homozygous form, the pearlscale
trait does not always express. If it does express, the reflective
characteristic of the scales doesn’t show up very well against the
black coloration. Pearlscale will be more apparent in the black lace
phenotype than in a black or hybrid black.
Veil tail is a partially dominant trait that will result in
lengthening and broadening the tail, and in lengthening the dorsal and
anal fins when present in heterozygously (V/+) to produce a veil tail
angelfish. When present homozygously, the tail and fins are further
lengthened to produce a super veil tail.
Phenotypes resulting from Black + pearlscale or veil |
Alleles |
D/+ |
D/D |
D/M, D/Gm, D/g |
St/+, St/St |
Streaked Black Lace |
Streaked Black |
Streaked Hybrid Black |
p/p |
Black Lace Pearlscale
|
Black Pearlscale |
Hybrid Black Pearlscale |
V/+ |
Black Lace Veil Tail |
Black Veil Tail |
Hybrid Black Veil Tail |
V/V |
Black Lace Super Veil Tail |
Black Super Veil Tail |
Hybrid Black Super Veil Tail |
Links
to more information about black phenotypes
Dr. Joanne Norton, FAMA: July 1984; Vol. 7, #7
Dr. Joanne Norton, FAMA: May 1989, Vol.12, #5
Approved by The Angelfish Society
Standards Committee on February 11, 2007.