Shiro – Graduate level   (Judges)

  We have covered in a 101 class ;

1)      The mutation of shiro

2)      The concept of base color

3)      The difference between selective bred shiro and natural mutation shiro

4)      Hard white and soft white skin

Moving up to an even more in-depth understanding,  I’d like to introduce to our student judges the different genetic  types of shiro and how they make our koi very  different fundamentally.

The nishikigoi clan can be sliced and diced in many ways.  The most fundamental way being by their base colors.  ZNA teaches us that koi are eitheir black based or white based.  And this should be of no surprise as nishikigoi rises from magoi and specifically from Asagi magoi ( giving us white base) and also from Tetsu magoi ( giving us black mutation colors and also a different ‘branch’ of shiro/pattern).

  Asagi magoi is so important because it carried both black and white base.  The hyper-melanistic  forms rising in the later Karasu clans and the Narumi asagi leading towards the true Leucistic forms.

  These two avenues represent the ‘breaking out’ of combined mutation traits of white and black into two separate, yet parallel lines of change. And that in turn gave us two very different types of shiro.

  To take the next step in Shiro study we need a bit of a genetics conversation – As just mentioned,  Shiro in nishikigoi comes about from two very different sources/ways. And as far back as the 1960s the Japanese breeders knew of at least one of these sources as evidenced by the creation of white within the karasugoi clan and its systematic breeding program.  This line of primitive black fish represents the extreme of hypermelanism yet it is also the best phenotypic example of a certain mutation gene.

 This in fact is first shiro we can discuss. This gene is what the Japanese breeders called “the white spreading gene” and what modern geneticists might call the modification gene or the Epistatic gene. This  white gene in effect ‘covers’ the real color of the fish! Put plainly, The base of the fish is black yet the white spreading gene expresses itself in place of the base color. This domination represents a hypostatic or suppression of the greater  color and inhibits the expression of that color gene.  To summarize, this white spreading gene covers and inhibits the true base black color of a koi.  We see this demonstrated nicely in the progression from hypermelanistic crow to hajiro to hageshiro to kumonryu to shiro utsuri (in one of the two forms it exists in).  As the white gene spreads over the fish, the fish becomes progressively whiter until the matsukawa bake and shiro utsuri look similar to white based derived specimens gotten thru another gene/route.

  The second shiro, recognized as a more valuable shiro, is not from the spreading gene. But rather from another natural mutation or expression of Leucism.  In this case, we have the skin itself drained of all color and when reinforced by a pattern mutation know as Pie bald gene, the effect is quite amazing!  This is a dominate trait in dorsal patterned fish like kohaku  but can ‘disappear’ in some of the offspring.  Yet it is still carried by the black fish into the next generation. It is this complex that brings us BOTH black based fish (carrying shiro but basically black and mutations of black such as red) and true white leucistic specimens or white based fish. And as these two strains are isolated we see white based fish with dorsal patterns of piebald with very refined white skin AND we see black based fish like the showa, express Leucism within the skin as they age.  This is a case of incomplete dominance when no piebald pattern is exists. Instead this gives rise to the wrapped pattern of base black partially replaced with mutation black (red) and shiro from Leucism. And interestingly enough, a DIFFERENT look to shiro utsuri than the other Leucism ( the white spreading gene) brings us!  This is WHY there are two very different looks to shiro utsuri and to the amateur seems like the MOST improved of all fish after the Gosanke. In truth it is a different source of shiro and easier to improve than the spreading gene shiro’s.

 If you study the white of the two forms of shiro (spreading and pure Leucism) and add the piebald pattern and understand the wrapped pattern ( interplay of shiro on sumi)  and its genetics, you will begin to understand koi from a higher level and likely appreciate the nishikigoi even more that you did before you studied these two variations of shiro gene expression.    JR