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Thread: Genetics and Koi

  1. #1
    Honmei ricshaw's Avatar
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    Genetics and Koi

    I was out in my garage, and I happened to peek in a box that contained some of my father's old stamp collection.

    Under the stamp stuff, I found some old BKKS magazines that an old former Englishman Koi club member gave me.

    I found four like this:

    Genetics and Koi-genetics_3836.jpg

    Genetics and Koi-genetics_3835.jpg

    Genetics and Koi-genetics_3834.jpg

    Just for fun, I thought that I would share one article I scanned.

    GENETICS AND KOI
    J. Smartt, Department of Biology,
    Building 44, The University, Highfield, Southampton.

    It would be ideal if there was a sufficient fund of genetical knowledge for the geneticist
    interested in koi to offer some kind of genetic counselling service for koi breeders. This
    however is not the case, and the reasons why it is not, are not very clear. There is a book
    'Genetics for Aquarists' by Dr. J. Schroder which gives good coverage of mostly tropical
    ornamental species, koi and goldfish are not covered, There is an illustration of koi; Kohaku,
    Sanke, Bekko. Asagi, Ohgon. Hi-Utsuri, a nice selection of different varieties but not a word on
    their genetics! What then is the problem? Why should it have been possible to sort out
    reasonably satisfactorily the genetics of the guppy but not that of the koi or goldfish. Some attempts have been made on goldfish genetics and some progress has been made but more
    problems remain than have been solved. The situation is perhaps even more difficult in koi
    because of the different emphasis in selection and the very distinctly different outcomes. In the
    goldfish variation has been selected in colour and scale type as in koi (where these are the basis
    of the whole wealth of variation we see) but also in body, form, finnage, the eyes and the
    hypertrophies of the head --the hoods of lionheads and orandas and the pompon of the pompon.
    The complexity of colour differences in the koi is of a totally different order of magnitude to that
    of the goldfish. This of course means that it is very difficult to know exactly where to start. The
    obvious answer is to start at the beginning!

    One aspect of variation in koi which is reasonably well understood is the inheritance of
    the 'German' scale or 'Doitsu'. It seems that one dose of the 'German' allele gives mirror or
    other large scales, while a double dose produces a great reduction in the number of scales
    resulting in the leather carp. This is favoured by carp-farmers on the continent because
    preparation of the fish for cooking is easier. This is somewhat at the expense of vigour and
    vitality, a point to he borne in mind when comparisons are made between wild and ornamental
    carp. The mutations carried by ornamental forms do depress viability and vitality to a degree,
    fortunately koi are still remarkably vigorous.

    Probably the best strategy to follow in determining genetic control of colour is to attempt to
    retrace as far as possible the evolutionary sequence in the development of the wide range of koi
    varieties. It is generally agreed that the original carp to be domesticated were wild carp taken
    for food production in stew ponds. Mutant forms differing from the wild type in colour may have
    been spared their progeny, selected for enhanced colour development. This probably resulted
    in the red or yellow-gold forms which were known in the trade before World War II as Hi-Goi, These relatively early developed forms could he crossed to wild carp and the mutations
    which had occurred could be determined by genetic analysis. This could be done progressively
    perhaps along the lines of the Genealogical Chart of Masamoto Kataoka ('Live Jewels’ General Survey
    of Fancy Carp, Masayuki Amano).

    Some comment on this chart generally might he appropriate, some of the progression seem to
    he surprising to say the least, varieties which look rather similar are widely separated (Hi-goi, Ki-goi, Ohgon) and the same type, e.g. Shiro-utsuri seems to have arisen in two different lines. It would be interesting to see how different two (superficially at least) similar lines were genetically, e.g. Shiro-bekko and Shiro-utsuri. It would be necessary to establish the progeny characteristics of bekko x bekko and utsuri x utsuri initially.

    According to Matsui, koi can be considered in two groups, monochromes and patterned and he states categorically that patterned forms tend not to breed true, he does not explicitly state that the monochromes do. However any parental stock or strain used in a genetical study would have to be tested and its breeding behaviour understood. The monochromes Shiro Muji, Aka Muji and Ohgons would probably be a good starting point. These could be crossed with each other and the type of segregation produced studied. If few different types were produced this would indicate close genetic similarity, if many, then more complicated differences probably exist. What might well turn out to be a relatively simple difference is that between Gin Rin scaling and the common scaling in Kohaku and Sanke types for example.

    One of the most intriguing problems genetically is that of the Kohaku pattern and colouring, not only, because it is the most highly prized type but because from Kohaku x Kohaku spawnings one can apparently get such a diversity of other recognised varieties of kol plus goodness knows what else. It might be worth trying to see if it were possible to produce high proportions of Kohaku type progeny by crossing selected segregants from Kohaku x Kohaku matings (e.g. Shiro Muji x Aka Muji).

    We appear to be in a position that some at least of the most highly prized koi varieties are unfixable. How can this come about'? It is often the case that the desired form (phenotype) is a heterozygote, this is totally unfixable, but 100% heterozygotes can be produced if you cross the right homozygotes.

    Another problem which can arise is aneuploidy (i.e. less than the complete chromosome complement). This has been reported from Japan (1981) by Ojima and Takai, in which odd numbers of chromosomes have been reported in Ohgon, Kohaku and Sanshoku (Sanke or Showa) 2n = 99 instead of 100+. The Chromosome number reported for carp vary around the 100 mark, with up to 104 being reported. It would be useful to have confirmation that chromosomes have actually been lost in the Kohaku or what changes in chromosome structure have occurred, this would certainly explain why Kohaku don't breed true if they, of necessity, have a complement of 99 chromosomes. Aneuploidy can only be tolerated in polyploids, that is in organisms which have complete extra sets of' chromosomes. This gives them spare genetic capacity so that loss of a chromosome or two may be tolerated easily. The loss of chromosomes in a diploid, that is an individual with the normal complement of chromosomes, is usually lethal.

    Talking of lethals it is also possible that some colour genes may be lethal when homozygons — recessive lethals, and some have been reported in carp. The only viable individual which expresses the colour character is of course the heterozygote which cannot obviously breed true.

    It is appropriate to say something about the chemical basis of colour and its visual texture in koi. The major determinant of colour is of course melanin which is a black/brown pigment typically. It produces pigmentation not only in fish but mammals including ourselves. It can exist in two forms eu-melanin (black) the darker form and phaeomelanin (brown-melanin). Melanins can be responsible in mammals for the whole range of colours from black — yellow (albino, in total absence of melanin). In fish the compound guanine can also be involved in pigment production, xanthine (yellow) and other pigments can be produced along with it Guanine has another role in producing the metallic lustre of some varieties and it forms a backing material of the scales, in addition it can be deposited in the body wall and the lining of the body cavity,

    Mutation can affect what happens to the guanine and melanin, when and if they are produced, how much and how they are distributed. The formation of these compounds is a multi-stage process, each step of the way controlled by a different gene, mutations of different genes may well produce different effects, altering the amount and nature of the final product.

    CONCLUSION

    This all too brief survey has indicated the broad nature of the difficulties of koi genetics and some possible causes of these difficulties. An approach to investigating koi genetics would need to bear the following in mind:

    1. Only progeny from controlled matings should be studied, hand-spawning gives the best control.

    2. A reasonable sized progeny is necessary, not just a few dozen, a few hundreds or a thousand or so is preferable.

    3. Effects of environmental selection and competition must be minimised.

    4. Simpler genetic differences should be analysed first.

    Bearing these in mind good progress could be achieved.

    The Magazine of The British Koi-Keepers’ Society, August 1986, Volume 12, No. 4

  2. #2
    Daihonmei MikeM's Avatar
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    I have several of the old BKKS bulletins. They make a fun read, giving a window on the roots of the hobby in the West. Good find, MCA.

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