Moscow & Japan Blue Swordtails

Moscow  & Japan Blue Swordtails

© Alan S. Bias

Permission granted for nonprofit reproduction or duplication of photos and text with proper credit for learning purposes only.

What is the value of maintaining your swordtail females as tail neutral you may ask?  Compatibility, not only for use with multiple Swordtail strains maintained in your fishroom, but also for out crossing with other tail shapes in creation of new swordtail phenotypes.  From a simple perspective, they can be used with just about any Y - linked gene complex to guaranty similar expression in the F1 generation.


Around 2005 I acquired some super Purple Moscow Deltas from Marty Lawson in Virginia.  This line was truly purple in color.  Not a dark black with hints of purple color, or a shade of blue that appeared purple in certain lighting.  Just Deep Purple ~ OK, couldn't resist that one. I ran them for several generations before lack of space came into question.  By that time my newly expanded  fishroom was again filled to with Swordtails.  What to do with a line of deltas?  Well if I turned them into Swordtails they would not be just taking up space.

F1 Purple Moscow Delta * Lace Snakeskin

F1 Purple Moscow Delta * Lace Snakeskin

Assuming most of the Moscow genetics involved being Y-linked, in my mind, it was a simple process of selecting the best neutral females available.  So I began by breeding Purple Moscow * Lace Snakeskin & Vienna Lower females.  As a rule my Vienna females will pass extension & outcrosses result in some sort of lower sword.  The Lace Snakeskins seemed like most European lines with swords resulting from a combination of  X - link for top & Y - link for lower.  So the resulting F1 really suprised me.  Nearly all the males exhibited a colored caudal with moderate length double swords. Evidently, the females used in the cross had passed on X-linked genetics for double swords.  The base body color in the F1 was either blue or purple with matching caudal & dorsal color.    

F1 Purple Moscow Delta * Lace Snakeskin

What was even more suprising was how much X-link color was passed to the F1 daughters by the sire.  At the time I  knew very little about the makeup of a female Moscow.  It quickly became apparent X-linked Moscow traits from this line were not only influencing caudal / dorsal color, but also body color from the dorsal to peduncle.  This would provide some interesting results down the line in 2 or 3 generations.  From this point forward I basically sib bred these fish for several generations  to see how things would recombine.  The blue phenotype would prove much easier to maintain vs. the purple.  While metal clearly showed in the shoulders, it was not matching the body color.  Even so, the Moscow had passed on at least partially as evidenced by this.  You can see in the caudal & dorsal a similar shade of color .   F1 males had full color between the rays with this phenotype.  None were clear, except at the very trailing edge of the roundtail.

F2 Purple Moscow Delta * Lace Snakeskin

Now for the fun part.  Earlier I mentioned that the Moscow females were having  a strong impact on pattern, similar to half blacks,  in combination with how the colors recombined in the later generations. The result  in the F2 was as close to a true half black swordtail as I have ever come across.  Attempts to fix this phenotype met with mixed success.  While I could produce them with regularity each generation, using this type of male did not fix to type.  So I figured it was random recombination, more than my use of this phenotype to sire the next generation.  Another interesting observation is the length of the swords and dorsal.  Males were near identical and always had a defined "clear" area between the swords.

F3 Purple Moscow Delta * Lace Snakeskin

While some males still had the original caudal shape, by the F2 / F3 I had succeeded in producing a nice thick double sword, as seen in the top male on the left.  Some had a clear area between the rays, but many did not.  A caudal shape very similar to H Turrason's Coral Red Albino Double Swords.  In fact, this may have resulted from use of coral red, which I then maintained, but without my notes I unable to substantiate at this time.

F2  JB * Lace Snakeskin

Parallel to the above crosses I also did a JB * Lace Snakeskin cross.  This met with great success from the start.  By the F2 I had a nice looking lines of double swords.  As expected the JB overshadowed the Snakeskin in the body, but left visible expression in the caudal and dorsal.  This was a very nice looking line of doubles with a caudal shape and color reminiscent of their European Lace Snakeskin ancestry. 

F1 JB * Vienna 

Another little project I had going at the time also involved Japan Blue.  The original males were pretty much wildtype JB with short clear round caudals and  with no colored rays or extension.  Multiple attempts at creating a lower sword via   JB * Vienna matings produced to little avail.  It seemed the JB gene complex would suppress extension in my Vienna line females.  Dorsal Color was easily influenced.  If I bred the same females to a non JB wildtype male with any type of short sword, upper or lower, it resulted in an F1 with extension on a regular basis.   I probably gave up on this project too quickly considering how many nice lines of JB Lowers have been developed by Asian and European breeders since.  Yet, sensing this was a long-term project that would need the commitment of many tanks I ceased my efforts after two or three generations.

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