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Monday, September 2, 2013

Homozygous Asian Blau Vienna Emerald

Homozygous Asian Blau Vienna Emerald
© Alan S. Bias
Permission granted for nonprofit reproduction or duplication of photos and text with proper credit for learning purposes only.
Sept 2, 2013
Homozygous Asian Blau Vienna Emerald

Likely one of the least appreciated guppy phenotypes to be found is Homozygous Asian Blau (Ab).  Such fish  are normally considered weak by-products of popular delta breedings involving blue iridophores and red color pigment;  Blue Topaz, Blue Grass, Half Black (HB) Neon quickly come to mind as examples.  Each strain is created by the removal of red color pigment, frequently an X-link, from phenotype.  It is still contained in genotype, only masked via epistasis.

Is this a good enough reason for show breeders or those researching specific traits to casually discard such an unassuming phenotype?   Can these fish be of use to IFGA and other showing breeders programs for research and improvement?  Most assuredly, by fostering an understanding of genetic principles from an extreme perspective, In turn increase iridescence in solid color pigment strains such as red, green, blue and purple.  It can also lend a better understanding into the complexities of modern platinum strains, which in conjunction with Ab, are now frequently infused into solid strains such as modern Yellow Delta’s.

Homozygous Asian Blau Vienna Emerald female

We can ascertain red pigment is not actually removed, as it returns in sibling breedings and outcross to non-red color pigment strains.  This indicates red color pigment remains present in genotype of  homozygous Ab & heterozygous Ab individuals.  European breeders routinely refer to this practice of using Asian Blau as a “Blau cheat” to artificially create “Blue”.  Ab in the prior examples should be looked upon as nothing more than a genetic tool for removal of red color pigment.  It is no different in practice than outcross to a non-red strain; only in genetic principle does it differ.  For the most part yellow color pigment, while sometimes reduced, is normally left intact with infusion of Ab.

Homozygous Asian Blau Vienna Emerald
In all strains, to include prior examples, homozygosity for Ab will reduce male caudal structure in X-link Caudalis Pigmentierte (Cp) Delta Tails, Y-link Lower Swordtails (LS) and X-link Double Swordtails (DS) to a shape resembling a roundtail with extension. Though, some weak delta tails present, more often than not homozygyous Ab definitely has overwhelming impact on Cp.  

Again, this is via epistasis and not removal of affected traits.  In example:  I routinely test breed homozygous Ab Vienna Emerald LS, as pictured above, to non-Ab or heterozygous Ab sisters.  The resulting heterozygous Ab or non-Ab male offspring exhibit 100% Vienna LS phenotype with full extension as in photos below.  While sons homozygous for Ab continue to resemble their sire.  If find it very intriguing that Ab can have little or no effect on dorsal extension.  This further lends support that most caudal and dorsal extensions are independently regulated, unless in true complex.

Asian Blau is considered an “Autosomal Partially Domiant Trait”.  Simply stated, it expresses to a degree, ie. alters phenotype, in heterozygous fashion.  In my Vienna Swordtail breedings this occurs in at least  three primary expressions;  removal of red pigment, reduction of black melanophores, and amplification of iridophores.  This is visibly manifest in both grey and blond (IFGA gold) fish to nearly equal degree.

Vienna Emerald Lowersword
Heterozygous Asian Blau Vienna Emerald Lowersword
The focus on this article is to point out to breeders that homozygous Ab expression can be used as a case study, resulting in a form of beauty with fertility and hardiness.   In turn, can be used in heterozygous form by those breeders with visual acuity to further advance strains.  For further reading on heterozgous Asian Blau expression you may wish to read:

Infusion of Ab into strains bred for predominantly flat color pigment over iridophores can result in heterozygous Ab phenotypes with extreme eye appeal as given in example and seen above.  Breeders often combine additional autosomal recessives for pattern modification requiring homozygous expression; fragmentary snakeskin, Z-bar, metal (Mg), blond (b), albino (a), pink (Pk).   

Autosomal Partially Dominant Traits are often much weaker standalone in homozygous form than traditional Autosomal Recessive counterparts, such as golden (IFGA bronze) or albino.  When Ab combines in homozygous form, in conjunction with additional homozygous recessives, it can result in weak or stunted fish.   Linebreeding is not advisable.  While traits such as golden are considered recessive, they do, in fact, visibly alter expression in heterozygous form.   

Homozygous Asian Blau Vienna Emerald
Homozygous Ab is no different than any other homozygote expression.  It requires diligence on part of breeders to both bolster hardiness and phenotypical expression.  One way to accomplish this requires a breeding program geared toward iridescence over color pigment, and yellow color pigment over red.  As mentioned Ab will not remove yellow pigment in finnage in heterozygous form, but homozygous Ab will.  Leaving visible only certain classes of black melanophores and metallic iridophores in; blue, red/purple, yellow/green.  This will create a genotype allowing for colorful expression.    
Luteus (by Winge)
Research has shown yellow color pigment has a close relationship with black melanophores in multiple recognized complexes.  It is easily seen in traits such as Luteus (Lu) and Flavus (Fla).  End result, when one is present so is the other.  In delta strains this often manifests in the form of black trailing edges on finnage in strains such as grey body HB Yellow or Yellow Deltas.  In blond (IFGA gold) counterparts melanophores are reduced, leaving areas devoid of black.  Yellow Swordtails express no different, and the effect is often more visible resembling wild-type

Flavus (by Winge)
While heterozygous Ab will in effect remove black from phenotypical expression in these traits, as evidenced in prior heterozygous grey Ab Vienna LS photo, it can have just the opposite effect in homozygous expression.  It will both collect and amplify regions of black.  The addition of variegation, a trait involving black melanophores, is also disrupted by Ab.  As is Nigrocaudatus (HB) and Cp.  In each case, there is a correlation with a disruption of the expected effects of a specific trait in conjunction with Ab.
Flavus - Ni - Cp (by Kirpichnikov)
Concentrated black melanophores in homozygous Ab fish are also highly motile in nature.  This extends to all zones of regulation in body, caudal and dorsal.  While masked via epistatic effect of homozygous Ab, yellow color pigment is still very much present in genotype.  As regulation is controlled in several distinct body segments, each independent of the other, expression can vary immensely from minute to minute when courting or feeding.  In analogy, a poor man’s Cuttlefish if you will.

With effort Homozygous Ab guppies, while unlikely to ever place in a sanctioned show, can have a beauty of type all to themselves in the realm of established strains.  I have always thought of them as incorporating the wispy and delicate form found in Japanese “Medaka”.  Of much more importance is the ability of Ab to educate visually inclined breeders and show the results of “cause and effect” found in their Ab show Guppy strains.  All it takes is a little patience, knowledge and a good eye. We are often so pressed for space on a quest to save and select superior breeders for the next generation; we fail to digest what those who fall short have to offer.
Homozygous Asian Blau Vienna Emerald

Color Plate References:
Winge, O  & Ditlevsen, E. (1947), “Colour Inheritance and Sex Determination in Lebistes”, Carlsberg Lab, Copenhagen, Valby.
Kirpichnikov 1981 – “Genetic Bases of Fish Selection”, Translated by G.G. Gause, Springer-Verlag, Berlin Heidelberg, New York.

Guppies have always been referred to as a Geneticists Dream. One day our Genetic Toolbox will likely realize a finite number of traits to work with.   For now they keep appearing around the world in breeder tanks in ever increasing combinations.

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Click on blog photos to enlarge