Betta genetics is a fascinating and absorbing aspect of keeping these beautiful fish.
In this article, we will discuss two of the recent color types that are enjoying huge popularity among betta hobbyists: metallics and masked bettas. Breeding metallics and masks is undoubtedly an enjoyable hobby, but the mysteries of these two traits have yet to be fully understood.
What are metallics?
Metallic betta fish have a glorious iridescent sheen. Iridescent colors most commonly seen are steel blue, royal blue, and turquoise. These colors occur because of the light reflection from thin, crystal elements that are present on the surface cells (iridophores).
These colors are often referred to as structural colors, to distinguish them from pigmented colors, such as black and red. It was discovered by Dr. Rosalyn Upson that wild betta imbellis, as well as copper and metallic bettas, contained iridophores that reflected a different part of the visible spectrum – yellow to yellow-green wavelengths – and can, therefore, be classified as a “new” yellow iridophore color.
What are masks?
Masked bettas are those where the iridescent or metallic body color extends across the betta’s head and face.
Meet Dr. Leo Buss
Dr. Leo Buss PhD is a Professor of the Department of Geology and Geophysics at Yale University, Connecticut. Dr. Buss has also authored many articles for the “Bettas and More” column in the FAMA Magazine, and has given several discourses on betta fish genetics for the International Betta Congress, (IBC).
Dr. Buss’ interest in metallic bettas has led to some interesting discoveries.
In one experiment, Dr. Buss used an electron microscope to look beneath the metallic layer to the colored layer that the metallic scales were obscuring. Based on Dr. Buss’ findings and some experimental breeding by several keen hobbyist breeders, it’s now possible to draw a clearer picture of masked and metallic bettas.
That’s the first step on the long road to understanding what these fish are and how cross-breeding them can affect the other colors.
Findings of Dr. Buss’ experiments
Dr. Buss examined several betta imbellis from different genetic lines under a microscope to try to determine their “wild-type” state. All the wild betta imbellis that were examined displayed yellow reflecting iridiophores in the distribution noted in Dr. Buss’ FAMA article. In this article, Dr. Buss suggested that there is a gene that inhibits the spread of any metallic coloration, which he dubbed the “no metallic spread” or “NMS.”
Dr. Buss’ betta breeding experiments appeared to indicate that the gene could be a simple Mendelian recessive. He also used a “+” notation (implying a “wild” trait) for metallics such as copper, noting that the gene was recessive to the Bl (blue) gene.
Without the + gene, the copper betta fish were simply a steel blue color, the blue/green (“teal”) betta was royal blue, and the dark metallic green betta was turquoise.
Dr. Buss also noted that although both the masked and metallic genes originated from the hybrid crosses, they were not the same, and each type could exist independently of the other. That is what makes fully-masked, solid color, pure iridescent blues not only a very real possibility, but within easy reach in a matter of a few generations.
Dr. Buss states that the metallic influence can be bred-out by the F4 generation, although many breeders are of the opinion that, once the masked gene is introduced, it is virtually impossible to get rid of it completely. Even after several generations of out-crossing bettas to non-metallic, i.e. pure iridescent fish, breeders were still seeing the blue lips and parti-masks that are characteristic of hybridization.
Breeding copper bettas
Solid copper/gold bettas are genetic steel blues; therefore, breeding copper x copper will always produce 100% copper fish.
Exceptions to that rule do occur in those spawns that have another recessive gene, such as marble. For example, take a look at these interesting results:
- Copper/gold x turquoise green: all green with variable metallic expression present
- Copper/gold x royal blue: blue/green and grass green, all with variable metallic expression present
In one especially interesting breeding experiment, a copper/gold betta was crossed with a melano. The resulting spawn was all green with variable metallic expression. Some of the fish were more turquoise in color than others, although all were within the spectrum of green.
Bearing in mind that copper/gold is + over steel blue with no melano gene, you would expect to see 100% steel blue offspring from this spawn. However, because of the fact that a fish that is heterozygous for the metallic trait still displays the metallic phenotype, the yellow-reflecting iridiophores that are present give these fish a greenish tinge.
The variation of the metallic expression exists partly because the quantity and spread of the yellow iridophores is variable between fish, and also because the crystals that are contained within the iridophores vary in size.
Other Experiments and Variations
One breeder crossed a copper/gold betta to a yellow betta. The intention of the experiment was to see how the + gene would affect red and non-red. The result was fascinating:
- Copper/gold x yellow: Gold scale reds, green/red multis (like imbellis), Cambodians
- F2 (green/red multis): Gold scale reds, Cambodians, Yellows, Green/red multis
- F3: Brass (gold body, red fins)
Also, the breeder crossbred Copper/gold with:
- Opaque, producing platinum
- Red, producing metallic red
- Cambodian, producing metallic Cambodian
- Black lace, producing black/green and black/copper
- MG, producing metallic MG
Looking at the results of all those matings, it can be deduced that the + gene does not work as a recessive that needs two carriers for + in order to appear. However, the + gene affects other colors in more subtle ways from the very first filial generation.
The masked trait
In regular iridescent bettas that do not carry the + gene, the fins, and body of the fish are green, blue, or steel. Also, their heads are usually black or dark brown.
Breeding to metallic generally introduces the masked gene. That causes the fish’s body color to spread into the face and head areas of an iridescent betta, producing a true, solid-colored fish. That masked effect can work independently of the metallic gene. It can also be reduced in expression, meaning that you can have a copper-gold fish with a solid, dark-colored head. Or you’ll get a color that’s increased to the extent that it covers the fish’s head and body, resembling a suit of armor.
You can also breed to metallic to get the masked trait then remove the metallic gene. If you also keep the mask through selective breeding, the result will be a solidly iridescent fish.
The pluses of the metallic gene
Iridophores of various sizes in the crystalline layer of the fish’s skin cause the characteristic metallic/copper iridescence. In bettas where the coloration is pure iridescent steels, greens, and blues, the iridophores are all the same shape and size, producing the normal iridescent appearance.
The different sizes of the iridophores in metallic bettas affect how light is refracted. That’s one theory used to explain the color changes that can be observed in metallic bettas.
One effect of the metallic gene on other colors is that it can produce a “whiter” white opaque. It can also achieve a more intense extended red by thickening the color and causing it to spread over the fish’s face and head. The metallic gene can also produce a more intensely black melano. It covers the iridescent color that’s usually faulted in black fish through the effect of the reflecting yellow iridophores.
An extremely iridescent black betta would appear to be copper-bodied with black fins, rather than steel-bodied. A good melano with just a minimal amount of iridescence will appear to be very solidly black. Interestingly, the reflective yellow scales of some metallic black bettas may eventually flake off, leaving a flat, dark black color underneath.
The metallic gene has produced a glorious variety of the most stunning betta fish ever seen. Their beautiful colors reflect the light and dazzle the eye. There’s just one cause for concern. The “old” color lines will be lost entirely if breeders don’t make a concerted effort to preserve them.
That’s because the + gene affects the outcomes of crosses so profoundly. Therefore, it’s critical that hobby breeders strive to keep pure lines of reds, yellows, iridescents, melanos, and opaques, and more that are completely free of the + gene.
Used responsibly, breeding and crossbreeding betta fish with the + gene is fascinating and fun to do.
Just how many new colors can you create? That question still needs to be answered. But all betta hobbyists are sure to have a whole lot of fun finding out!