Cross 1

Snow white and halfblack blue guppy crossbreeding

Purpose: The first deliberate outcross to begin the program to restore the snow white phenotype.

Male (Gandalf):

  • Bought from a big box store during February 2023 as part of the initial stock.

  • Strain: Snow White

  • Relevant genes. Some are assumptions, indicated with italics. Although their decedents strongly support the claims:

    • Base body color: Blond (bb)

    • Magenta: likely homozygous (MM)

    • European Blau: (rr)

    • Stoerzbach: (ss)

    • Nigrocaudatus: (XⁿᶦᴵY)

Female (Female #1):

  • Bought from a big box store during February 2023 as part of the initial stock.

  • Strain: Unknown

  • Relevant genes. Some are assumptions, indicated with italics. Although their decedents strongly support the claims:

    • Base body color: Gray (BB)

    • Magenta: likely a non-carrier (mm)

    • European Blau: (RR)

    • Stoerzbach: (SS)

    • Nigrocaudatus: likely homozygous (XᴺᶦᴵXⁿᶦᴵ)

Crossbreeding results from a snow white and halfblack blue guppy

Offspring:

  • Born: May 14, 2023

  • Brood Size: 32

    • 12 Male

    • 20 Female

  • There were two distinctive phenotypes:

    • Group A: Halfblack with a red tail (22 guppies).

    • Group B: Non-Halfblack with a clear-ish (female) tail or a tail with splotchy red patterns (male) (10 guppies).

  • Phenotypical distribution of 69 to 31 percent between group A and B respectively. This suggests that a recessive allele is likely at play here. It’s interesting that the halfback seems somewhat tied to the guppies showing more red which makes the heterozygous halfback genotype of female #1 questionable, although not impossible.

  • Likely genotype(s) following the order of the listed genes for the parents:

    • The Halfblack-red-tails: Bb|Mm|Rr|Ss|(XᴺᶦᴵXⁿᶦᴵ or XᴺᶦᴵY)

    • Non-Halfblack with clear-ish tails: Bb|Mm|Rr|Ss|(XⁿᶦᴵXⁿᶦᴵ or XⁿᶦᴵY)

  • Notes:

    • I initially did not know if the female was homozygous or heterozygous for the gray-based body color. Because all of the offspring were gray-based, this suggests that female #1 was homozygous for gray-based body color.

    • I initially did now know if the female carried the magenta gene or not. It seemed safe to assume that she didn’t because magenta looks to be an incompletely dominant gene and I could not find any signs that she expressed magenta.

    • European blau was a gene I only became aware of during Cross 5 but it seems to be important in these crosses. I’m not 100% convinced that it is European Blau but so far, the data seems consistent.

    • I initially thought female #1 was homozygous for halfblack but her offspring suggests that she wasn’t. There are two versions of this gene and I am assuming that Nigrocaudatus I is the one responsible here and is carried on the X chromosome.

    • Two of the halfblack red females were used to backcross to Gandalf (Cross 6). These females are labeled Cross 1 Female A (C1AF).

    • Two of the non-halfblack females were used to backcross to Gandalf (Cross 7). These females are labeled Cross 1 Female B (C1BF).

    • A YouTube video detailing this cross can be found here.

Snow white and halfblack blue guppy cross result phenotype

    • I kept one of the males in a spare tank out of curiosity. The picture above was taken on March, 8th 2025, just shy of 2 years old. The photo was taken under bright light which washed out quite a bit of the red but he generally looks similar to the male on the bottom left in the previous image. I am not sure where this phenotype comes from genetically but I think it propagated into Crosses 7 and 11. A video clip of this male appears in my Cross 13 Part 3 video here.