My research about Kohaku is still going on with as much passionate as those first days. Although I have shifted my interest a bit to “irregular red pigment distribution,” the mystery of Kohaku coloration is still an attractive question mark. A few months ago, when looking back those clip and pictures of green Marble swordtail offspring that I used to breed sourcing from Mr. Nekoba, a sudden question came up in me that urged me to Mr. Trochu inquiring about the origin of his Marble swordtails (You will find Marble swordtail very fascinating in the below pictures). After being explained the way Marble swordtails created, I spent extra time gazing at his fish pictures, then realized something in common between the two lines; Something is much of consistency, rather than just a common name “Marble”. So, I pasted all pictures on the same page and start sketching my thoughts, which you could see briefly below in this post. Marble, came from the cross of Hamburg swordtail to Red swordtail represent the interference of black pigment and red pigment, which is dominant in each strain. So, when they are expressed on a single body, they (black and red) started to overlap consecutively, or more accurate, they competed to each other showing distinguishable area of strong expression; or in other words, their competition revealed the areas of origin. On those pictures to the left of Marble swordtails, I drew some black arrows pointing the place where black pigment really invaded and dominant over the red, besides the black lateral pigmentation line along the fish body. Those area would also mean where the red pigmentation be weakest; as the matter of fact, black pigmented area isolated and bring up the areas of red origin. Recalling about my analysis 2 years ago, when I hypothesized that the red coloration is controlled by some genes of a family: 1) Red cap [Hr] gene: express from top head, extend to mouth, gill, neck, chest, then pectoral fins. 2) Dorsal red [Dr] gene: express from high back, around body down to belly, up to dorsal fin if being strong enough. 3) Red tail [Tr] gene: express from caudal peduncle covering lower body till anal fin, also may extend to caudal fin if being strong enough. Now, it seems to me the Marble pattern did support my hypothesis: “Following that suggestion, popular Kohaku Koi phenotype [Red-White-Red] is assumed to be the loss of function in Dr gene [Dr-]. As the matter of fact, when being under strong expression, Hr or Tr gene may cover part of Dr expression region, even overlapping each other, but a suppressed Dr [Dr-] always show a triangle of white pattern as shown in the second picture below. Source:https://ctswordtail.weebly.com/blog/kohaku-koi-swordtail-coloration-hypothesis-based-on-phenotype-observation#comments” From the angle of research by observation-based data, my hypothesis would be very limited support, but I hope in the future I could hand on genetics research technique to decode the mystery of Kohaku swordtail. (to be continued…)
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Kohaku Koi is always occupying my mind with a huge interest. However, there's not much information about them so far, like their origin, possible phenotypes / polymorphism, and underlying genetics mechanism that created such a cool creature (in my opinion). So, while keep searching for their archive, waiting for more research data introduced by other breeders, I would like to do something ... such as proposing a hypothesis from my observation on Kohaku strain. Although Kohaku Koi swordtail is collectively suggested as a Red and White swordtail model based on their color development (see Red and White swordtail classification by Mr. Rainer Rekord), I still feel very eager to explore more of the mechanism that controls Kohaku coloration because in my opinion it is pretty far different from the one of Piebald swordtail. Here is something I would like to share to fellow breeders: - Kohaku Koi is known as a recessive color gene. However, by observing popular phenotype [Red-White-Red] from my line development as well as from many other breeders' line, I would suggest that Kohaku phenotype is pretty much caused by the loss of function in Red pigment production gene. The suppression of this gene is likely stopping red pigment to be expressed in skin, thus exposing a large white pattern on the host body. - As proposed by some research documents, the red coloration is controlled by some genes of a family: 1) Red cap [Hr] gene: express from top head, extend to mouth, gill, neck, chest, then pectoral fins. 2) Dorsal red [Dr] gene: express from high back, around body down to belly, up to dorsal fin if being strong enough. 3) Red tail [Tr] gene: express from caudal peduncle covering lower body till anal fin, also may extend to caudal fin if being strong enough. Following that suggestion, popular Kohaku Koi phenotype [Red-White-Red] is assumed to be the loss of function in Dr gene [Dr-]. As the matter of fact, when being under strong expression, Hr or Tr gene may cover part of Dr expression region, even overlapping each other, but a suppressed Dr [Dr-] always show a triangle of white pattern as shown in the second picture below. Red cap phenotype (picture #3): In a rare case, we see a phenotype called Red cap, which is only Hr express on the host body, both Dr and Tr are suppressed. And if never before you found a true Kohaku Koi with milky white head without any red spot, would you think Hr gene is lethal when under suppression? Orange blossom phenotype (picture #1): I saw some people called a non-standard Kohaku Koi (with white spot at stomach) as Orange blossom. But from my experience, this phenotype showed 100% when you cross a pure Kohaku Koi to a Red swordtail in purpose of increase redness of the Kohaku strain. That meant the F1 phenotype is heterozygous Kohaku Koi [Dr Dr-]. When this phenotype happened in F2, I would consider those individuals to have low vibrant Red pigment production, and are often culled out because F3 (by interbreeding F2) resulted very bad Kohaku pattern. (to be continued...) Talking about Red-White swordtail, Mr. Rainer Rekord suggested a classification of 5 types based on the region of red pigment allocation along the body of the swordtail as the following:
The combination of III, IV and V can have the same effect as II (white belly). Variants I, II and the two combinations can expand and combine different. Until the red covers the whole body. Therefore, this breed animals may have little red. (Source: https://www.facebook.com/groups/swordredwhite/) The gallery below is just an example of color region that red pigment may consistently express on the swordtail body (no matter which strain of swordtail that you could identify.) Thanks to Mr. Rainer Rekord for his observation. I myself found that the classification system is very helpful to understand Red and White patterns in swordtail strains. Yes, there're a couple strains (in fact, different genes) that express various patterns. Personally, I would explain the system as following: 1. Pinto, Peppermint or Pieball strain: Type I: Usually see red pigment express on the lower body, extending along lateral line, forward as far as to the gill, yet narrower, and backward to the caudal portion. As describing by Mr. Karl Trochu, he had another strain that he had obtained from Mr. Darrell Mefford in 2006. It produces 'all white', 'bleeding heart' (mentioned by Mr. Rainer Rekord above), as well as as red-spotted offspring. The juveniles fish change color several times before they reach maturity, making this strain a very interesting one to work with. Type II: Pieball irregular patches between red and white. This is rare, but I tried to find a picture to depict this type as in the gallery above. Variant I & II: See picture above 2. Kohaku Koi or Santa claus swordtail: When it says Koi swordtail, please don't mistake it with the Red eye Kohaku. Koi is a separate trait of color expression, representing Red and White pigmentations, while albino is about the loss of black pigment in the eyes thus resulting Red eyes (the body also suffers this loss, making the white band of Albino Koi swordtail look milky white color). In other words, you would find Kohaku Koi with Black eyes also. Type III: Red cap. The gene seems to priorly express on the head cap, then extend its red pigment further to the back, wrapping around the gill, chest, but not the belly. Red cap only is a rare phenotype produced by Kohaku Koi. As the matter of fact, the cross between two red cap would yield a higher chance of red cap in offspring. 3. Red Saddleback or Pineapple swordtail: Type IV: usually see in Pineapple strain with Red pigment cover the dorsal fin, high back (saddleback) down to the tail. 4. Red and White swordtail: Type V: commonly called red and white swordtail (may be an ambiguous name), but easy to specify by finding the red pigmentation to express in the lower body part upto caudal portion. The upper body part and head is often offset white or light blue (under light). The most thoroughly studied group of fish for the genetics of sex determination are the platyfishes and swordtails of the genus Xiphophorus (for detailed reviews see Kallman, 1984, Kazianis et al., 2004 and Volff and Schartl, 2001). These fish nicely demonstrate the variability of sex determination systems in fish.
In the platyfish, X. maculatus, three different sex chromosomes: W, X, and Y occur. Females may have WY, WX or XX genotypes. The males are either YY or XY. Interestingly YY males are fully viable and fertile, indicating that no essential genes have been deleted during the evolution of the Y. WW females have not been found in natural habitats, but can be produced in the laboratory and are viable as well. Sex determination in this three chromosome situation is explained at present by two different hypotheses: The first ( Kallman, 1984) proposes a network of male determining genes and regulatory genes distributed over the different types of sex chromosomes and autosomes, while the second ( Volff and Schartl, 2001) favors a dosage dependent mechanism based on one gene being present in different copy numbers on the three types of sex chromosomes. The stable sex chromosomal determination mechanism in the platyfish can be overridden by rare alleles of autosomal modifiers found in some natural populations (Kallman, 1984) and by exogenous influences, e.g. X-ray irradiation (Anders et al., 1969) and steroid hormone treatment (Dzwillo and Zander, 1967). For the green swordtail, X. hellerii, some strains have been shown to be WZ–ZZ ( Kazianis et al., 2004) while others exhibit a so-called polyfactorial system ( Peters, 1964), meaning that the sex-determining genes are spread over several chromosomes, which additively or cooperatively influence gonad development. Other species like X. variatus and X. xiphidium appear to exhibit a simple XX–XY sex determination mechanism. A modification of the XX–XY system is described for two species, X. nezahualcoyotl and X. milleri. Most males are XY and most females are XX. However, a second Y chromosome, Y′, exists, which together with an autosomal modifier is responsible for XY′ females. Consequently, YY′ males can be produced ( Kallman, 1984). Another modification of the XY system was found in X. nigrensis. In this species all XY fish are males. There is an autosomal locus with two alleles, A and a, which affects sex determination in XX fish. If the genotype is AA, the fish will be female, and if aa, the XX individual will be male. Aa genotypes are predominantly female, but sometimes (approx. 5%) such fish develop into males ( Kallman, 1984). Attempts towards isolation of the sex determining gene(s) in Xiphophorus are underway. BAC contigs starting from marker loci that flank the sex determining region on the X. maculatus X and Y chromosomes have been established covering at present approx. one megabase on each side ( Froschauer et al., 2002). Source: A comparative view on sex determination in medaka 1. All fancy strains of swordtails (Xiphophorus hellerii) have mixed ancestries with Xiphophorus maculatus (moon platies) and/or Xiphophorus variatus (variatus platies). 2. The first Xiphophorus helleri showing an elongated dorsal appeared in the late 1950's in one of Mrs. Telma L. Simpson's fish tanks. This housewife turned fish breeder kept working with that single male until she fixed the trait. It is from her South Californian hatchery that it all started. In the 1960's and 1970's, top breeders developed all kind of fancy strains of both swordtails and platies… up to today. The most famous (to named a few) are Dr. Joanne Norton, Fred Morita, Glenn Takeshita, Rosario Arijon, Darrell E. Mefford, Bobby Ellermann, and Dr. Roy Levine. To read more about the complete history of hifin swordtails, read Mr. Ellermann’s most excelent article: 3. Two low-fin swordtails (that is fish with regular dorsal fin) will NOT produce hifin offspring, even if they have hifin parentage in their blood line. If they were to, then one would have just duplicated Mrs. Simpson’s original hifin mutation. If not technically impossible, still highly improbable... I have lately been made aware that Greg Sage of selectaquatics.com from Colorado has raised a strain of HIFIN Xiphophorus Mayae, so the gene mutation has once again naturally expressed itself. 4. Two hifin swordtails will always produce a small percentage of low-fin offspring. As far I know, there is no homozygous hifin for the Xiphophorus genus. Also a cross between low-fin and hifin swordtails produces roughly 50% hifin offspring. 5. SAILFIN swordtails are nothing more than a 'descriptive label' for HIFIN swordtails possessing an elongated dorsal fin with more branched rays, hence producing a sailfin looking dorsal (both wider and longer). Think of them as 'la creme de la creme' in breeding hifin swordtails. Such specimens seem to posses a genetic modifier allowing their dorsal ray to branch out. At least it is my limited understanding of it. 6. How are "sailfin" swordtails produced? Simply by selective breeding, culling, and hard work. The genetics of hifin swordtail is complicated and yet not fully understood. It is clear that if a strain of sailfin swordtail is not drastically maintained, it quickly regresses to producing more basic hifin fish. If one wishes to understand more about the genetics and science of hifin swordtails while viewing photos of splendid fish, then simply visit Dr. Levine’s website… everything you ever wanted to know and/or understand about hifin swordtails is there. 7. American Livebearer Association which is an organization worth belonging to if one is interested in livebearers in general. Most members are more into wild livebearers, but a few dedicated breeders of fancy Xiphophorus are still hanging around. A FEW LINKS OF INTEREST: - Dr. Roy Levine - http://www.xhifin.org/ - An authority in genetics of Xiphophorus fancy finage, and a true hobbyist at heart. His results and photos speak for themselves. - A great hobbyist breeder; of fancy Xiphophorus: Ela from Poland: http://xiphophorus-ela.blogspot.com/ - German website dedicated to Fancy strains of Xiphophorus: http://www.platys.net/ - An inspiring senior fancy Sail-fin swordtail breeder - Mr. Karl Trochu: http://miamiswordtails.weebly.com/ - If you are interested in wild and/or fancy xiphophorus, feel free to join this specialized Facebook's page:International Xiphophorus Breeder - French Livebearer Association: http://france.vivipare.free.fr - German Livebearer Association: http://www.guppy-molly-xipho.de/ To anyone who is seeking for quality specimens, two commercial breeders who produce exceptional fish are recommended by Mr. Karl Trochu " If I had to get any livebearers, I would get them from those two hatcheries, period!" - http://selectaquatics.com/ - Greg Sage form Erie, Colorado - USA - http://goliadfarms.com/ - Charles and Susan Clapsaddle from Goliad Texas - USA This post is credited to Mr. Karl Trochu and his website at http://miamiswordtails.weebly.com/ |
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