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  • Results 1 to 6 of 6

    Thread: Doitsu Lethal Gene and whether to use a fish in breeding or not.

    1. #1
      lifeoffaith's Avatar
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      Doitsu Lethal Gene and whether to use a fish in breeding or not.

      So, as some of you may remember, I had a flock spawn last fall and have a few babies that actually hatched. I think for a couple of reasons, I lost the majority of them.

      The first and most likely reason is that the mother I suspect to have been involved (no others lost any "weight" after the flock spawn) is a beautiful Doitsu Hariwake. I suspect that I had a bunch of eggs that died due tot he Doitsu lethal gene.

      The second reason is that it got quite cold right after the spawn, so I think that may have affected the eggs.

      My question is whether or not I should use my Doitsu Hariwake in a controlled spawn, or if I should just assume that I will lose a ton of eggs. I'm trying to gear up for spawning season here and plan on breeding 4 pairs, but I am still determining which.

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      Billy Pounds is offline Senior Member
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      Austin, i thought the death gene kicked in after the eggs hatched into free swimming fry and that is how it happened here....did you use methylene blue in the water with the eggs pre hatch???? Billy

    3. #3
      lifeoffaith's Avatar
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      I did not. I was under the impression it happened before the hatch.

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    5. #5
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      I suspect the issue you saw had little to do with the mother being Doitsu. Some here may have more insights on this matter, but according to the technical paper at:
      http://www.fao.org/docrep/005/b3310e/b3310e14.htm by V.S. Kirpichnikov,
      "Carp with genotypes SSNN, SsNN and ssNN are not viable. N gene is lethal in the homozygous state and embryos die in the hatching stage."

      I gather from this paper that all living Doitsu koi (whether leather or linear scaled) carry the 'Nn' gene pair. If they were NN, they would have died at hatching. If the were "nn" they would not have been Doitsu.

      So when crossing Doitsu koi together (whether leather or linear scaled), the odds of any one embryo being 'NN' are 25%. I bred Doitsu koi together a couple of years ago, and saw lots of dead fry on the bottom among the eggshells left behind. But the vast majority of the fry seemed fine. I still have 5 of the two year olds (two of which are Doitsu and three are not). Of course on the day of hatching I could not have counted the tens of thousands of fry (dead and alive), but the 25% dead on arrival figure seems about right.

      Note that of crosses Doitsu with non-Doitsu koi have no "NN" possibility, because the non-Doitsu koi has no "N" to contribute. Since you had a flock spawn, you could roughly approximate your "NN" losses by multiplying 25% by the percentage of males in the your pond that are Doitsu.

      The technical paper I mentioned above also gives the percentages of scale types you can expect from the fry of a given pair of parents. If you are trying to get Doitsu koi, crossing Doitsu koi can increase your percentages of those, as the table in the article shows (but you do forfeit 25 percent from the start).

      Matt

    6. #6
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      Cool, thanks guys, maybe it was just the cold then. I wasn't prepared for the spawn, so I didn't even have the water ready which means I had to fill up the tank with hose water which would have been considerably colder than the ideal temp for eggs, even after the bucket they were transferred in floated for awhile for acclimation purposes. I'm 90% sure mother was doitsu, father was standard scale. I'm pretty sure I only had the one male in the pond at the time that was old enough and the female doitsu suddenly lost a lot of weight, while all the other fish remained unchanged.

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