Blue Swordtails Japan
© Alan S. Bias
Permission granted for nonprofit reproduction or duplication of photos and text with proper credit for learning purposes only.
|Mixed tank of pure JB and JB * |
When a new strain of guppies or a variation upon one makes an appearance it can seem natural to credit its existence on newly discovered genetics. Occasionally this is the case. More often than not after careful test breeding and analysis the truth is revealed to be new combinations of already identified genes.
A year and a half ago I once again gave in to the appeal of Japan Blue (JB) and a chance to work with this alluring phenotype. My first hands on experience with JB came back in 2004. I started with a typical grey wild-type strain with a clear roundtail lacking extension or caudal color. Combined with females from an X-link Lace Snakeskin Double Sword strain it was easy to produce, and then fix a nice line of Variegated (Var) JB Double Swords after 2-3 generations.
Variegated (Var) JB Double Swords
Over the last couple years a line of Japan Blue Swordtails has been making the rounds on Aquabid. Inquiries with several sellers as to origins were met with the same vague responses that hinted to importation from Asian Breeders. What drew me to this strain were two particular traits: 1. First and foremost they were swordtails to varying degrees. 2. Second intense iridescence and what appeared to be more than normal blue coloration into the anterior portion of the body.
Accepted theory states that JB was initially identified as a Y-link mutation found in a feral population of wild-type guppies in
. Infrequent crossover to X-link has since been identified in a few strains. Blue patterns in guppies is not limited to expression as a result of JB. Recently, in Venezuela, French breeder Frederic Nicole collected a stunning new blue phenotype in a population of Endlers Livebearer. Blue covers the upper quadrant along the entire length of the peduncle and then some. It seems to have more in common with Lazuli than Japan Blue. In my fishroom there has been only one suspected instance of X-link JB in the last 10 years. Interestingly, the incident involved ½ a dozen males in a single drop of about 12 males in total from a Schimmelpennig Platinum Double Sword * Lace Snakeskin Top Sword breeding, and not an isolate individual. I had culled the dam prior to sons coloring up and worse failed to capitalize on the potentially X-linked JB type pattern for lack of tank space at the time, or so I decided. This was a very poor decision in hindsight. Japan
In any JB strain the pattern is almost exclusively ½ body with a clear line of demarcation starting just below the base of the dorsal fin, or slightly before, and running the length of the peduncle. The exact location often seems relevant to the level of improvement found in a strain. There also seems to be a direct correlation between Emerald Green Iridescence (EGI) determining how much the pattern bleeds into the caudal.
Other factors can influence the intensity and shade of blue coloration found in a Japan Blue male. The addition of yellow pigment in the body from genes such as vitellinus (vi) can modify appearance from blue to green or even yellow. The addition of red pigment can dilute from blue to lavender.
Blond JB *
Lower with X-Link yellow and metal Vienna
Based in part on these facts the perceived increase in blue coloration into the anterior portion of the body in this JB strain should result from additional additive effect or other genes. Not the JB itself.
In brief email correspondence I requested only males exhibiting a very long lower sword and if possible dorsal color of any type. The seller obliged on the first request, but was unable to provide any males with dorsal color as the strain did not have any. My initial approach would be several generations of sib breeding to identify existing traits in pure form. This revealed a percentage of males expressing “blue lips”. Colored lips are often found in metal / platinum strains. These males also tend to express the most intense blue and increased level of coverage. Males exhibiting a lower sword would generally pass the trait to sons to varying degrees in shape and length.
Japan Blue male with hyaline dorsal
In multiple purebred litters over 3 generations a portion of males would posses lower swords and a portion fairly mismatched double swords. The reminder being clear roundtails. This indicated not all the JB females were homozygous for producing or enhancing sword shape. Many of the roundtails and lower swords also showed oculatus (oc) spotting. Sib breeding also produced about 25% males with a red shoulder stripe. The presence of Zebrinus Bar (Ze) was evident as secondary sex link colors started to manifest in young males. This was quickly covered over as JB made its appearance. At the time, while suspecting it to be autosomal dominant Zebrinus Bar (Ze), I could not rule out autosomal recessive Tigrinus (Ti).
Autosomal Zebrinus Bar, as later identified
Less than 1 in 10 males would exhibit some patchy black dorsal color. Purebred sib breeding also told me the hyaline (clear) dorsal resulted from a lack of X-link dorsal color or it was epistatic to any existing genes for dorsal color. Therefore, likely near impossible to eliminate without outcross. Hence, making an outcross with my Vienna lowers a logical choice as they posses both Y and X-link for yellow pigment and gold iridophores in caudal / dorsal and to some degree. At this point I discontinued pure breeding the strain with better lower males resembling the individual below.
Blue Lower Sword with hyaline dorsal Japan
Reciprocal outcrosses to my Line 1Vienna Lower lines helped substantiate several developing theories about this JB strain. It showed JB females were actually contributing not only to caudal fin length, but the overall shape itself. Results hinted at fin extension being mostly X-link for swords, regardless of type. Notice that I say extension and not the sword itself. Sib breeding of F1 Vienna Lower * JB revealed in the F2 and F3 via recombination, that the foundation JB females often only carried extension on a single X-link or non at all. I note that not a single incidence of bar has occurred in my Line 1 Vienna Lowers in over a decade, though I breed for it regularly in my Line 2. Reciprocal crosses between JB and Line 1Vienna Lower showed the barring to be autosomal dominant Ze as it appeared in both directions of F1 offspring. So this should eliminate further consideration of Ti as the source of barring.
Lacking tanks space for breeding the double swords I have culled them for the most part. While I have done a few test breedings to evaluate, outcross with Vienna Lower females and recombination in the F2 / F3 hinted at two forms of doubles. The best matched possibly resulting from a single X-link and another resulting from a combination of X-link top sword and X or Y-link lower sword. The latter version likely in complex as no pure Top Swords have ever presented.
Segregation and recombination in F2 / F3 crosses (from both reciprocal crosses) in addition to F1 *
backcross (BC) revealed two concerns. First and foremost the JB Y-link lower sword does not appear completely dominant to either type of double sword or recurring clear roundtails, though the latter phenotype has been reduced in occurrence. I would not be surprised if better defined test breedings of doubles found them to be epistatic to lowers as is common with Vienna Swordtails. Second, optimal lower sword shape is not exclusively controlled by Y-link alone. Suggesting JB X-links &/or autosomal input for sword shape and length. Vienna
The continued use of Line 1 Vienna lower females for BC creates an issue all to itself. It produces JB males that are a definite shade of Apple Green or a blue with distinct regions of yellow pigment or gold iridophores.
F1 Grey JB *
Lower with X-Link yellow influence Vienna
Two of the first traits I wished to test for / rule out were Stoerzbach and Lazuli. I see no evidence of Stoerzbach to date. While I rule out Lazuli as unlikely, I do see similarities to this trait; 1. Blue coloration in the upper shoulders of some males. 2. Variation in shades of blue on individual males in distinct regions.
Reciprocal outcrossing to my Line 1 Vienna Lowers has revealed the true secret to this strain. This being the presence of autosomal Asian Blau (Ab), which is partially dominant. It not only helps add to the additional anterior color, but the overall color itself.
I. Abab (heterozygous) Asian Blau
II. AbAb (homozygous) Asian Blau
III. abab (non Asian Blau)
I. Unlike European Blau (Eb), Abab heterozygotes can express yellow pigment and possibly gold iridophores in body and finnage when the genes are present.
Blue with X-link yellow Japan
II. AbAb homozygotes remove / inhibit red pigment to reveal silver (or white) or blue depending upon the type of irridophore lying beneath the color pigment. As Japan Blue is a mutation of blue irridophores it seems there should be little or no silver in the peduncle. As seen below in grey form, AbAb fish appear blue/grey and in blond double recessive white. Epistasis likely prevents formation of swords and colors are limited to blue iridophores, possibly a theoretical gold as evidenced by the presence of green in the body.
Homozygous Asian Blau
Blue (Grey on left & Blond on right) Japan
III. abab Japan Blue males (those lacking the Asian Blau gene) may show a red stripe on the shoulders or caudal outside the region of influence in traditional JB.
Japan Blue lacking Asian Blau
Reciprocal crosses with Vienna Lower * Abab JB females show they also pass extension genetics to the F1 males. With selection this enhancement has been easily retained to a high degree in F2 and F3 sib-breedings. Having worked with Y-link lower swords for many years I am of the opinion that the best length and shape is only possible in combination with the additive effect of X-link &/or autosomal genes. I believe this is often taken for granted by many swordtail breeders working predominantly with X-link double or top swords in which the majority of extension genetics are also passed in a tight linked gene complex.
Few if any colors / phenotypes are the result of a single gene in guppies, more likely multiple genes by regulation(s). The initial reciprocal breeding involved my Line 1 using a Blond Vienna Lower * JB. It produced predominantly Abab males in both green and purple body mutation. This high degree of autosomal dominance has maintained in subsequent Vienna breedings. It likely expresses similar in JB. You will notice below in these Asian Blau Vienna Lower normally “Orange” Wingean spots are still visible, with red pigment removed, solely by remaining iridophores which are the basis for patterns. Prior to outcross my Line 1 Lowers did not contain Ze, yet barring is present in these F1 males. Thus, further evidencing the trait was passed by JB females as an autosome.
Another visible trait found in both my Line 1 and the JB, is a very blue belly patch. Resulting from blue iridophores it has been little modified by the presence of Ab. Passed by males and females, this trait helps ad to the additional anterior color of the JB strain in combination with Ab. A similar related effect can manifest above the lateral line on the shoulder. However, it is more often evident in conjunction with a blue belly patch.
Asian Blau Vienna Lowers w/blue belly
The male below is multi generation pure from my Vienna Lower Line 1. There seems to be a correlation between expression of the blue belly trait and EGI. You will notice in this individual how the blue is also found in the lower peduncle.
Normal non Asian Blau Blond
Lower w/blue belly Vienna
One of the hypotheses I wished to test for was the presence of Wild-Type Wingean Super gene traits being masked by Japan Blue. To do so I employed a simple “fright test” and moved males directly from their tank into my photo tank without a period of acclimation. You will notice that these males immediately revealed an orange spot in mid body. While not visible in this photo a second spot was also present in the peduncle.
Japan Blue males without period of acclimation
Within this JB strain in any given litter, both purebred and outcross with Vienna Lower, exists a broad range of phenotypic expression. The overall basis for both the increased level of coloration and its intensity in this strain results from Asian Blau (Ab). Additional color enhancement comes from a “blue belly” created by blue iridophores in conjunction with EGI. A lack of yellow pigment or gold iridophores in the body further enhances coloration. Each trait is independent of traditional Japan Blue (JB) and results from either X / Y sex link or autosomal genes.
Blue with X-link yellow Japan
Asian Blau Japan Blue with X-link yellow, including blond on the right
Enjoy the strains you have labored to create? Pass them around so others can do the same and maybe further your efforts. Never know when you might want some back …