Guppy Designer – Do guppy genetics really matter?

By Philip Shaddock

Originally Published on Guppy Designer Website

If you read the statements that are made on some English language forums, you would believe that guppy genetics does not really matter to the average hobbyist. This blog will address the most common arguments against the study of guppy genetics.

1. Nothing is known about guppy genetics.

The claim is that guppy genetics is so complex and so little studied that there is just no good information on it.

Obviously the person making this statement has not read Dr. Øjvind Winge’s paper published in 1927 (Winge, Ø., 1927  The location of eighteen genes in Lebistes reticulatus.. J. Genet. 18:1-42). This paper describes the guppy’s sex system, male only inheritance of Y-linked genes, eighteen patterns found on laboratory guppies and their mode of inheritance, selective breeding for a trait and theories about gene interactions and more. In fact, if this paper, now more than eight decades old, were carefully read by the average guppy breeder, there would be a new explosion of interesting and unique guppy strains. The account of genetic crossover alone would have people racing to their fish rooms to try out this “forgotten” genetic knowledge.

There follows many, many papers documenting guppy genetics. Natali in Russia discovered the half-black gene and wrote about its inheritance in 1939. Goodrich published an interesting study of the mutations of black color cells in the early forties (Goodrich H. B., Josephson N. D., Trinkaus J. P., Slate J. M., 1944 The cellular expression and genetics of two new genes in Lebistes reticulatus. Genetics 29(6):584–592). They called the two genes blond and gold, incorrectly described as gold and bronze respectively in North America. Again they described how it was inherited.They included microscope studies of the genes expression as color cells. The blond guppy is a mainstay of the hobby.

In 1959 Dr. Michael Dzwillo, curator of the Biozentrum Grindel and Zoological Museum at the University of Hamburg, presented the most comprehensive survey of domesticated guppy genetics at that time (Investigations of the Genetics of Domestic Strains, 1959). He describes the base body system used by modern European breeders and documents many of the genes found in modern strains (like the blau) and how they are inherited. His findings have provided important guidance for modern knowledgeable breeders. In fact I happen to have one of the strains he describes (the Istanbul) in my tanks right now, inbred for at least 60 sixty years. Perhaps one of the most talented and knowledgeable of modern breeders, Yoshiki Tsutsui (inventor of the Panda, Half-Tuxedo and Galaxy strains among others) specifically credits Dzwillo. He referred me to Dzwillo’s information on the mode of inheritance of the filigran (snakeskin) as a key to understanding many modern Japanese strains. This is a clear example of one of the world’s great breeders, Yoshiki Tsutsui, deriving his breeding programs from published guppy genetics.

I am sure that Penelope Nayudu, who recently retired, and is the author of two seminal papers on the biology and genetics of black patterns of the guppy would find the statement that nothing is known about guppy genetics rather surprising. Her work, written in the late seventies, is seminal in studying the relationship between genes and guppy patterns (Nayudu P. L., Hunter C. R., 1979 Cytological aspects and differential response to melatonin of melanophore based color mutants in the guppy. Copeia 2:232-242).

If people decrying guppy genetics would read just a handful of guppy genetics papers, some of the mysterious aspects of guppy genetics would be lit up like a light going on in a dark room.

Then there is Kirpichnikov who is shown in the above picture. Dr. Valentin Sergeevich Kirpichnikov wrote part of a chapter on guppies in his famous book “Genetic Bases of Fish Selection” an important guide based on scientific research in the early aquaculture industry in Russia and around the world. Kirpichnikov summarizes what is known about guppy genetics at that point (1979). His summary should be required reading for anybody who professes an opinion on guppy genetics, since it contains many of the keys to understanding guppy genetics. Just a dozen pages and the average hobbyist would have powerful genetic tools at their disposal.

I am in the process of writing a book that summarizes the field of guppy genetics and marries it to a study of many modern strains. The book is over 350 pages long, and I just skim the surface.

Is there anything known about guppy genetics? Lots. This is a fact anybody can check for themselves by doing a Google search on “Poecilia Reticulata” and “genetics.” You will discover that more recently there has been published excellent information on guppy genetics by the Max Planck Institute in Germany. I live twenty minutes from a guppy lab (the Breden lab at SFU).

2. Guppy genetics are special, they do not conform to genetic laws.

The idea that guppy genetics somehow breaks genetic laws is very common. Why study guppy genetics? It’s like nailing jelly to a wall. Nothing sticks.

I think it is safe to say that guppy genetics is not singularly unique and may not even be particularly complex. Color and pattern variability is a trait shared by Bettas, some African Cichlids, platies and swords, and goldfish among others. Guppies are just the most common model organism used in the study of what scientists call color polymorphism. I think the modern tools of molecular genetics and genomics will eventually crack the code. There is some promising research in Germany. And discoveries in related fields (particularly the zebrafish and medaka) may light up the field of guppy genetics.

Guppies are embedded in nature and behave according to natural laws. The mechanism that allows guppies to assume so many different colors and patterns is just not fully understood yet. To argue that there is some kind of random factor in guppy genetics that makes its study a useless exercise, or that it is too complex to ever yield to analysis, is simply an expression of ignorance of the work that is underway to cast light on guppy genetics.

A form of this myth is told about common crosses and their expected outcomes.  Guppy breeders will tell you that when common crosses (as between snakeskins and half-black guppies) are made they often produce unexpected results.You would expect a Dragon guppy to emerge from this cross, a guppy with a snakeskin pattern in the front of the body and a half-black pattern in the latter part of the body and spotted fins. But I know from my own experiments that the cross sometimes results in the complete suppression of the snakeskin trait by the half-black trait. Does this point to the futility of setting up theories about the outcome of crosses? No it just points out the futility of making generalizations that are not based on carefully recorded experiments between guppies whose genetics are known. There is no single half-black gene. The scientific literature indicates there are at least two half-black alleles. There are probably many more. And there are probably many snakeskin alleles. The work in teasing out the different half-black and snakeskin alleles just has not be done. (I am doing some of that work in my own fish room, including the Dragon guppy cross.) Additionally I am working on a theory that the snakeskin trait has variable penetrance, meaning it varies in its expression. It is probably made up of more than one allele. The fact that you do not get the expected result comes down to paperwork. You need to properly document the guppies involved in a cross. You need to work with strains that have known genetics. If you are a hobbyist without a great deal of knowledge of genetics or a fully equipped scientific lab, you simply need to follow in the footsteps laid down by Winge eight decades ago and analyse the outcome of crosses. It is not that hard! And it requires a basic grasp of Mendelian genetics.

In the end you will probably discover that the half-black pattern trait is due to many alleles, and once they are understood, the outcome of the crosses are very predictable.

3. Guppy genetics is esoteric knowledge and is not worth the effort or is irrelevant

This statement at least acknowledges that there is a body of knowledge about guppy genetics, but the statement denies its value. Or it implies it is too difficult to understand and therefore useless to the common guppy breeder.

I have seen various forms of this argument. One person compared knowledge of genetics to knowledge of the mechanics of a car and said, “my wife does not need to know how the engine works to drive the car.”

But this is the wrong argument. Guppy genetics is what makes guppy strains possible. Without guppy genetics you have a rather drab little fish that would probably still be in a jar somewhere on a scientist’s shelf. It is not a form of transportation that takes you someplace else. It is the journey itself.

The irony is that the guppy collectors and the show guppy competitors try to shoehorn the guppy into distinct strains. They place great value on a “truebreeding” strain precisely because the guppy is so genetically variable. Some of the more complex strains, like the Japanese Blue Galaxies, do require that you understand basic genetics just to maintain them. Otherwise they fall apart in your hands. I suppose there are people who hate to own things that require a manual, but I say they should not have bought into them in the first place.

I also think statements like “guppy genetics is esoteric knowledge” betrays a painful lack of natural curiosity. It is hard for me to imagine that you would not be at least a little curious about genetics if you breed guppies. And a little knowledge of guppy genetics can take you a long way. Instead people memorize the keeping of complex strains by rote or they simply re-order the strain from the original breeder again.

What is most special about a guppy is its genetics. The desire to play with its genetics is a very strong call to the hobby. Otherwise you might as well keep killifish or chickens.

A well known judge in a guppy organization once asked me “why do you bother with all this stuff about guppy biology and genetics.” I think he had been waiting to ask me that question, confident he would stump me or catch me espousing some line about the value of esoteric knowledge. But I saw the sneer fade from his face when I abruptly and spontaneously gave him an answer. “It is like being in the middle of an action mystery and not knowing how it will turn out.” He walked away muttering.

It’s like talent among artists, you either have got natural curiosity or not.

4.”I have never known a guppy geneticist that has raised a decent guppy.”

This statement was actually made by a well known guppy guru.

A “decent” guppy is presumably one that conforms to a judging standard. As it turns out the guru was one of the architects of this standard. In other words, the statement is only true if you accept the guru’s authority. It is circular logic. The guppy is only “decent” if it conforms to the standard I invented.

I think I will be the judge of that.

Engaging in guppy conformance competition requires memorizing a standard,  then selectively choosing the best males and females to meet the standard. Beyond that it is a trial and error undertaking. The more tanks of the same strain you maintain, the more likely an outstanding example of the standard will emerge. There is also some strategic thinking involved as you plot to win a class competition and acquire the guppy stock to do so. Like the study of genetics, it does require a certain amount of study and some blood, sweat and tears.

But the actual breeding methods are pretty basic. The most dominant form of breeding is simple selective breeding, where the biggest and best guppy is chosen from the hundreds of males and females in the tanks. The reason why award winning guppy breeders are so secretive about their breeding methods is because they are simple and easily repeatable. I am told by one of the top show guppy breeders that he uses simple formulas passed down from older breeders. But he was unwilling to share them. The skill comes in being able to select the breeders. Apparently some people are incapable of matching males in their tanks to the judging standard.

Guppy conformance breeding is a different form of the hobby than designing guppies with unique patterns and fin shapes. When guppy genetics is the hobby rather than the means to an end, it is free and open-ended. At its worst it is like found art, design by accident. Let’s put two guppy strains together and see what happens. Let’s follow the results. In its highest form it is a craft that rewards knowledge and skill. It results in the establishment of new strains like the grass guppies of Japan or the Neon Blue guppies of Singapore.

Case in point: the half-black guppy. It was first identified and documented by the Russian scientist Natali. It was refined into a show guppy through selective breeding.

Case in point the Japanese Galaxy and Panda strains. Developed by Tsutsui who studied genetics. Refined through selective breeding for the show bench.

Can you see the relationship here? Does that mean that the hobby of genetics and the show guppy hobby are separate and distinct?

Absolutely not. They just have different goals and different outcomes.

Genetics is after all simply the study of genes, and genes are the units of inheritance. A selective breeder matching guppies to a standard is not deliberately engaged in the study of genetics, but they are participating in a very crude way. When they pass around among themselves the information that a short stocky female will give birth to sons with short stocky bodies that are capable of holding up a large caudal fin, they are sharing information about genetics.

I once heard the aforementioned guru tell his disciples how to “fix a strain.” For example, if you have a male with a good dorsal, how do you create a strain around it? His method was expressed as: “Breed the father to the daughter, and then breed him to the granddaughter. After that breed brother to sister.” This is one of his “breeding secrets.” But I think it is a statement about genetics. You inbreed for three generations so that the maximum number of the original male’s alleles are inherited by his grandchildren. Hopefully in the process the genes governing the dorsal become homozygous. Once they are homozygous, 100% of the offspring will inherit the desirable genes. A “breeding secret?” I think not. Reading Winge’s 1927 paper would give you the ability to come up with this breeding strategy without the years of trial sight breeding requires.

The problem with such formulas is that they do not apply to all instances. For example, if the desirable trait is heterozygous, meaning it is due to two different alleles, then only a percentage of the offspring will breed true after the three inbreeding generations. Success will also depend on making the right choices about the female you cross to. I think it is easier to figure out wants going on at a lower level. That way, you can figure out what happened when things don’t go to plan and make adjustments. In this case it really does matter if you understand what is going on under the hood.

Does it not seem reasonable to assume that the more you know about genetics, the better you will be at manipulating your strain’s genetics? I would argue that a great guppy cannot be created without a great deal of knowledge about guppy genetics.

5. I am a sight breeder, not a geneticist

The inherent appeal behind this statement is that you rely your own brains and eyes for your knowledge of guppy inheritance, not on the evidence of others.

This statement flies in the face of several hundred years of science. Science is a methodology that tries to arrive at consensus by developing a consistent method for discovering the facts and then presenting them in such a fashion that other people can try to disprove them. Only after a theory has been thoroughly tested is it generally accepted.

The actual definition of “esoteric knowledge” is the knowledge of a secretive priesthood who have a special connection to the truth and specialized knowledge they do not share. It is precisely because this esoteric knowledge was used to stand in the path of individual freedom of thought that science rose to prominence. I regard information from so-called “sight breeders” as interesting and useful first hand witness accounts. But I do not think it is genetics knowledge. To me genetics knowledge is theory arrived at by consensus, shared knowledge that everybody agrees on because they have put the theory to the test. Until it does pass the test, the information from so-called sight breeders is rife with possible mistakes. It is information that is unreliable.


Do guppy genetics really matter? To the show guppy breeder and the guppy collector they matter because genetics knowledge makes you an efficient and knowledgeable breeder who can meet his or her goals more effectively. So rather than describe guppy genetics as different from collecting or showing guppies, I would say it is integral to both activities. By virtue of the fact that the guppy is polymorphic perverse (to coin a phrase) you will have to wrestle with how traits are inherited sooner or later. A short dorsal is considered to be an undesirable trait. Well, what are you going to do about it? You are probably going to find out how to “breed it out.” You can spend the next ten years trying to do so through trial and error. Or you can save yourself a lot of time and discover the genetics of dorsal length. (Hint somebody has already done the work.) The second approach is the path of knowledge, the first is brute force. Which do you choose?

Personally I do not need to justify the study of guppy genetics in this way. For me deciphering guppy color and pattern and genetics is like being in the middle of a mystery novel. And as soon as I put it down there is another mystery waiting…

I don’t think I can express it any better than T.S. Eliot, the English poet who describes that sense of wonder that an open and free mind experiences when they go over familiar territory again and see something fresh and new:

“We shall never cease from exploration
And the end of all our exploring
Will be to arrive where we started
And know the place for the first time.”

Philip Shaddock