I can hear some of you out there saying to yourselves, "If he wanted to create an albino black guppy why didn't he just out-cross an albino strain with a black strain?" Well, I have come to believe (for the time being, as far as I can tell, to the best of my knowledge at this time) that the phenotype "clear black" guppy is not a black colored guppy but a guppy that is wearing a black overcoat. I take into account that perhaps a black guppy is a guppy that carries an epistatic gene that causes the guppy to appear black. AZ defines "epistatic" as a gene that is able to mask the presence of one or more other genes. My hypothesis is that "black" is an epistatic gene that masks whatever color and tail pattern the guppy would exhibit if the gene for "black" were absent.
Black guppies can show up in the red tails as early as the F2 generation when pairs of CD red tails are mated. Black guppies can occur within the mosaic and cobra gene pools for no apparent reason they just appear. Does this then qualify "black overcoat" as Mother AZ's version of a mutation? I used to believe that I could create a black guppy by concentrating melanin. (In view of the fact that I was making heavy use of back-crosses at that time this speculation is now suspect in my mind, at this time.) Speculation, contemplation and theorizing about the nature of Mother AZ's black guppy do not provide answers. We gotta throw some into a tank and see what we can find out.
I have over a dozen strains of clear black guppies on file. I have added a notation to the strain name that lets me know from where each strain originated. For this "show and tell" I have selected a black strain with the notation "out of mosaics". (This rather mysterious notation tells me that this is a strain of black guppies I must have stabilized months ago before I realized that the term mosaic was so generic. Mosaic what? Tiger, leopard, grass? Heaven only knows what this strain really is, but it is black.) The albino strain I have chosen to use is the "albino clear pewter" strain we stabilized in the previous pool. Although it looks exactly like any other clear silver albino guppy, I know that Mother AZ considers the strain to be "pewter". (I also speculate that Mother AZ's silver and gray guppies are also epistatic in some way but that is another topic to investigate later.)
I have made the following observations concerning the "black overcoat" gene.
 The gene for "black overcoat" is not sex-linked; it can be passed on to the progeny by either dad or mom guppy. The gene for "black overcoat" is dominant to the gene for "no black overcoat".
The gene for "black overcoat" is not expressed by albino guppies and by some mechanism is not passed on to albino progeny by non-albino parents. (Albino guppies insist on swimming around naked?)
Here are the two strains we will be out-crossing.
I chose a male from the black strain and a female from the albino strain.
Here are the males produced in the F1 generation.
Every one of these guys is clear black. Dad's genotype for this trait was BB; mom's genotype for this trait was bb. All of these guys (and their sisters) have the genotype for "black overcoat" of Bb.
Mother AZ produced seven males but only one female in this generation. This presented me with the opportunity to produce one (just one, Don!) F1 generation from each male.
Here are the F1 generations produced.
Golly, where did all those colors and tail patterns come from? I did not include all the black males produced in each batch, but I did include all other males for you to see. My speculation is that every male with the "black overcoat" phenotype has two possible genotypes, BB or Bb. Every male that exhibits a color/tail pattern has the bb genotype.
My plan for this experiment is to select one of these F1 generations and start mating a "black overcoat" male with an albino sister for many generations. If "black" is an epistatic gene how will albino males exhibit the trait, if at all. AZ states that albinism is a typical example of an epistatic gene. Is "black" the reverse of "albino"? Goodness, the questions that continue to come to mind. Enough drivel! On with this "show and tell"!
I selected batch "B" because I liked the albino grass males it contained. Choosing a black male (again at random, not knowing if he is BB or Bb) I paired him with one of his albino sisters (definitely bb) to produce the F3 generation.
Here are the males in the F3 generation.
All the non-albino males are "black coated" (BB or Bb), however, the albino males are far from basic black or gray or silver. Moving on to the next generation I again selected a black male (BB or Bb)/albino female (bb) pair to produce the F4 generation.
Here are the males in the F4 generation.
"Grass olive green" and "albino grass topaz" are included in this batch. The appearance of the "grass olive green" males suggests that those males are bb for "black overcoat". This would of course be possible if the dad were Bb (no, that is not a musical B flat!). I proceed on to the F5 generation using a "black overcoat' male and an albino sister.
Here are the males in the F5 generation.
Dad must have been BB for "black overcoat". Do the albino males look clear black yet? Nope, now we see topaz tiger with enhanced mahogany stripes in addition to the grass topaz. Where is the black color in the albino males? Do you think that the albino males are showing off the tail patterns that the non-albino males are hiding under their black coats? We proceed to the next generation using a black male from this batch and an albino sister to produce the F6 generation.
Here are the males in the F6 generation.
I suggest/suspect that the color/tail pattern being hidden under the "black overcoat" of the clear black males is green grass/heterozygous for tiger and clear. I have no way of knowing what phenotype (color/tail pattern) the males wearing black coats have on under their coats, but it looks like the tail pattern has been grass or tiger. Moving on to the F7 generation of this experiment I again select a clear black dad (BB or Bb) and an albino sister (bb) to produce a batch to look at.
Here are the males of the F7 generation.
AZ produced no non-albino males in this batch. Works for me. I am ready to bring this demonstration to a conclusion. You can do this experiment yourself and take it out as many generations as you like. A "black coat" strain is very easy to stabilize and any stabilized strain of albino will suffice.
I was curious to see what was happening with the tail pattern in this albino strain so I continued to pair an albino "grass" male with a sister for several more generations.
Here are the males in the F8 generation.
Here are the males in the F9 generation.
Here are the males in the F10 generation.
Here are the males in the F11 generation.
Yep, just what I suspected all along. The grass phenotype is heterozygous for clear and tiger. I could switch to using a clear or tiger male at this juncture and quickly stabilize either clear or tiger strains in as few as two generations. In fact I did! I never fail to stabilize any strain that Mother AZ lets me have.
Not one to leave an avenue of discovery unexplored I returned to the F4 generation and mated one of the "olive green grass" males with two of his sisters, one albino and one regular. The male was suspected of being bb for "black overcoat". The albino sister used was known to be bb for " black overcoat". The genotype for "black overcoat" of the regular female was unknown. Here are the males produced by the "olive green grass male (bb)" and one of his albino sisters (bb).
As you can observe, the gene for "black overcoat" has been eliminated from the gene pool.
Here are the males produced by the same green male (bb) and one of his normal bodied sisters.
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