WHY DO GREEN-BLUE-PURPLE GUPPIES SUDDENLY APPEAR IN DEDICATED STRUCTURAL COLOR BREEDINGS?
Have you ever wondered why
Green-Blue-Purple Guppies suddenly occur in your dedicated breedings for a
single color? It’s all in the genotype…
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| Green Delta (pb/pb) and (Mgmg), expressing VEG modified to blue. |
© Alan
Permission granted for nonprofit reproduction or duplication of photos and text with proper credit for learning purposes only.
February 25, 2024
International Fancy Guppy Association (IFGA) Green-Blue-Purple
delta form a “continuum” of interrelated structural color expression. Other than Y-linked orange peduncle ornaments,
each lack sex-linked xantho-erythrophore (yellow-orange-red) color pigments in their
body and finnage.
Structural color derives from a thin basal layer of violet-blue
iridophores and melanophores residing in close proximity forming chromatophore
units. Actual expression is influenced several
factors, including the ratio between violet and blue iridophores. Further influenced by diversity in angles of
crystalline
platelets, which act as mirrors, residing under the violet-blue iridophore
layer. In conjunction producing variations
in perceived color, i.e. green or blue-green or blue or blue-purple or purple depending
upon angle of ambient light source.
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The primary genes at play include, but not limited to: Purple Body (Pb), Metal Gold (Mg), and Vienna Emerald Green (VEG). Each of which are conserved across multiple teleost species.
I. Purple Body
is a confirmed autosomal incompletely dominant gene that expresses in ratios of
(1:2:1) in genotypes (pbpb : Pbpb : PbPb).
Which equates to (non-Purple Body : heterozygous Purple Body :
homozygous Purple Body). What this means
is in perfect ratios, if all offspring survive to maturity, 1 out of 4 will be
pbpb, 2 out of 4 will be heterozygous Pbpb, and 1 out of 4 will be homozygous
PbPb.
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| Purple Delta (Pb/-) modified ornaments, expressing VEG, reduced xanthophores and increased violet-blue iridophores. |
Pb has visible effect in heterozygous expression and
amplified effect in homozygous expression. In heterozygous condition formation
and migration of xanthophores which result in yellow color are inhibited. In homozygous
condition formation and migration of xantho-erythrophores which result in
yellow-orange-red color are inhibited.
Pb is often present in both Green and Blue. Pb is always found in all-purple fish, but is
not by itself sufficient to produce the all-purple phenotype in heterozygous
Pbpb expression or homozygous PbPb expression.
While Violet is a true wavelength color, Purple is a composite produced
by combining blue and red wavelength colors. Further removal of
xantho-erythrophores, in conjunction with both increased populations
and/or the visibility of modified melanophores and naturally occurring
violet-blue iridophores, is required for production of the all-purple
phenotype.
II. Metal Gold appears to be an autosomal incompletely
dominant gene which would express in ratios of (1:2:1) in genotypes (mgmg :
Mgmg : MgMg). Which equates to (non-Metal
Gold : heterozygous Metal Gold : homozygous Metal Gold). What this means is in perfect ratios, if all
offspring survive to maturity, 1 out of 4 will be mgmg, 2 out of 4 will be heterozygous
Mgmg, and 1 out of 4 will be homozygous MgMg.
Mg has visible effect in heterozygous expression and amplified effect in homozygous expression. Though harder to quantify, in heterozygous condition formation and migration of xanthophores which result in yellow-gold color are often limited to specific regions of the body, such as the central caudal base, the dorsal and specific regions of the body. In homozygous condition the entire body appears to be additionally covered by a yellow-gold cast. As seen in Apple Green phenotypes.
Mg is present in both Green and to a lesser degree in
Blue. However, Mg is absent or masked in Purple. Mg expression is greatest
in pbpb, i.e. non-Purple Body, reduced in Pbpb, i.e. heterozygous Purple Body
and non-expressed or masked in PbPb, i.e. homozygous Purple Body.
III. Vienna Emerald Green is reportedly passed by
Y-link mode of inheritance, though I have seen several instances of potential
X-link in breeding tests. VEG is most
visible as a central green spot at the peduncle-caudal base, though should be
considered a full body modifier that exerts influence body wide.
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Vienna
Emerald Green (VEG) Peduncle Spot. |
VEG expression is greatest in pbpb, i.e. non-Purple
Body, reduced in Pbpb, i.e. heterozygous Purple Body and non-expressed or
masked in PbPb, i.e. homozygous Purple Body.
VEG expression is easily modified from green to blue.
Solid structural colored fish did not just occur in a
single event or in rapid fashion to suggest they result from a single dominant gene.
Rather, the result was a long cumulative
breeding process in which color pigment genes were removed and visible
Variegation (Var) in the dorsal and trailing edge of caudals persisted for many
generations. Suggesting “solid” is an actual
phenotype in which Var is still present and masked. Being comprised of multiple small mutations
in co-expression.
Such a hypothesis is supported by anecdotal evidence. Primarily in the form of visible results from
outcross breedings of Green-Blue-Purple to unrelated fish outside of this color
spectrum. Resulting F1 offspring always express
Var to different degrees in body and finnage.
Further support is garnered by another simple observation that is
indicative of the continued presence of Var in solid colored fish. That being, solid colored Green-Blue-Purple
fish always express a “black trailing edge” in the caudal and dorsal comprised of
motile melanophores. Which is suggestive
of chromatophores needed to produce Var pattern being disrupted in
co-expression and further repulsed to exterior edges of finnage. Together, each supports solid colored Green-Blue-Purple
fish being a true phenotype comprised of multiple gene expressions accrued over
time.
 (A) Green Delta expressing Pb modified ornaments (Pb/pb) and (Mgmg). (B) Green Delta (pb/pb) and (Mgmg), photos courtesy of Bryan Chin. Note the deepening of the orange body spots. Both males are expressing VEG. |
 (A) Blue Delta expressing Pb modified ornaments
(Pb/pb) and (Mgmg). (B) Blue Delta (pb/pb), photos courtesy of Bryan Chin.
Note the deepening of the orange body spot to pinkish-purple with Pb through xanthophore
removal (arrows). Both males are expressing VEG.  (A) Purple Delta (Pb/pb) males. Results of a homozygous Green (pb/pb)
male x homozygous Purple (Pb/Pb) female breeding. (B) Homozygous Purple
(Pb/Pb) male x homozygous Green (pb/pb) female breeding. This
type male will express as either blue or purple depending upon the angle of
light. Note partial modification of orange ornaments to pinkish-purple and increased
violet iridophores (red circles). Both males are expressing VEG.In summary, zygosity dependent, the presence or
absence, and concentration of Purple Body, xanthophores, and erythrophores is
the primary distinction in spectrum between IFGA Green-Blue-Purple structural
colored phenotypes. References: http://www.pr.bioflux.com.ro/home/volume-7-1-2017/ http://www.pr.bioflux.com.ro/home/volume-7-1-2017/ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Things getting out of hand in your fishrrom? Re-define your goals and narrow your focus to
obtain realistic results ~~~~~~~~~~~~~~~~~~~~~~~~~~~~ |
