Koi (Gold
Marble Blushing)
Non-wild
alleles that interact to form this phenotype:
Gold Marble (Gm), Stripeless (S)

The gold
marble blushing phenotype is probably best knows as a “koi.” The koi
angelfish is a gold marble angelfish with two doses of the stripeless
allele. A koi angelfish has one of the following genotypes:
Gm/Gm – S/S
Gm/g – S/S
The koi
angelfish gets its name from the combination of black, white and orange
coloration because these same colors are often found in the koi carp, a
popular pond fish.
A gold
marble blushing angelfish will have a white body with black
marble-patterned markings. In addition, it will commonly have orange on
the crown. The amount of orange coverage can range from being
completely absent to covering almost the entire body.
The orange
coloration has variable expression and is sensitive to environmental
conditions and stress. It usually can be seen in very young fry if it
is going to express, and will deepen as the angelfish matures. No one
has yet definitively identified which environmental factors play the
most significant role in achieving good expression of orange.
Adult koi
on occasion may completely lose their orange. This is generally
attributed to stress, but it may be difficult to pinpoint what causes
the stress, or to explain why some kois will lose their orange and
others will not under stress. Once lost, no one has reported seeing the
orange color return.
Some people
do not refer to a gold marble blushing angelfish as a koi unless it at
minimum has an orange crown. Some people will call it a koi regardless
of the presence or absence of orange coloration, basing the name on the
genotype more rather than the on the presence of orange coloration.
(For the sake of simplicity, the terminology “gold marble blushing” and
“koi” are used interchangeably on this page.)
When the
phenotype first became popular, breeders considered a good koi to be one
with a full orange crown. Through selective breeding, top breeders have
developed lines that exhibit ever increasing percentages of orange
coverage on the body, with some koi angelfish having almost 100 percent
coverage.

The koi
angelfish differs in appearance from a non-blushing gold marble in that
the non-marbled areas of the body are very white instead of the
off-white to pale gold of a non-blushing gold marble. As a fry and
juvenile, the gill covers of a koi are translucent, resulting a circular
pink color in the gill area, as lack of pigment allows the color of
freshly-oxygenated blood in the gill area to show through. As the fish
matures the gill covers typically become opaque, and the blushing will
no longer be seen. The dorsal and anal fins will have no horizontal
striations, and the tail will be smooth with no lacy patterning. In
addition, the adult koi often develops silvery-gold iridescent random
patches on the body, which result from deposition of guanine. These
iridescent patches will not be seen in non-blushing angelfish.
      
  
Approved by The Angelfish
Society Standards Committee on May 14, 2007.
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