marble betta

Marble Betta Fish: The Art of Breeding Marbles

Betta fish come in a dazzling array of forms and colors, each with a different back story and genetic profile. But there’s one betta strain in particular that hobbyists love, and that’s the marble betta.

So, where did the marble betta come from, and how easy, or not, are they to breed?

Origins of the Marble Betta

Orville Gulley is the official creator of the marble betta. He was a prison inmate who raised his betta fish in empty peanut butter jars. According to the story, Gulley was attempting to create a black butterfly betta when he discovered the marble gene completely by accident.

Gulley sent a few of his fish to well-known International Betta Congress (IBC) hobbyist and author of several well-regarded books on bettas, Walt Maurus, as well as to a few other breeders. Maurus and the other betta fanciers liked this new strain of fish and began breeding them for the pattern.  

Marbles are like the pinto horses of the betta fish world. They have dark, solid-colored blotches on a white or flesh-colored body or vice versa. The very first marbles were black and white. Since that time, the strain has developed into pretty much every shade imaginable. In the process of their evolution, marble bettas have helped to shape a great many of the new colors that are now possible to create in bettas.

Breeding Marbles

The marble betta is likely a partial dominant, although some believe that the trait is a partial-recessive or a co-dominant. So, crossbreeding a marble and a solid-colored betta fish will usually result in a spawn of mostly solid-colored fish, with a few marble-patterned bettas thrown into the mix. 

If the solid-colored parent betta carries the marble gene, the percentage of marbled fry increases. The marble gene influences the solid color in unpredictable ways, making new color and pattern combinations possible. That said, a breeder will most likely need to persevere through several generations and many culls, before achieving what he set out to do. Even after that, there’s the challenge to overcome of persuading the newly created color to breed true.

Crossbreeding marble to marble usually generates some dark-bodied solid colors, a few light-bodied solid colors, some marble, and some butterfly. The solid-bodied butterfly bettas derived from a marble spawn generally have the same inherent characteristics of a solid color that you get from a solid line. That is, when the butterflies are crossed with the same solid color that originates from a solid-colored line, the spawn will all bear a butterfly partial dominant gene.

Spawns of either dark or light-bodied solid color betta fish from marble stock will produce three different offspring colorations. They’ll always yield some solid color, some marble, and some variegated color fish. If the marble genes are introduced into a line of solid-colored, true-breeding betta fish, it becomes almost impossible for the breeder to return his breeding stock to the pure-breeding solid-colored strain. These fish always seem to produce a few particolored offspring or marbles. A crossbreeding of a marble stock betta of one color type may cause the marbling effect in the pattern of a betta of a non-marble type. 

The “Jumping Gene”

Recently, a discovery was made in the science of genetics. Researchers identified the existence of “transposable elements,” also known as “jumping genes.” 

What is it?

These “jumping genes” are capable of moving from one of an organism’s chromosomes to a different location on another. Sometimes, the “jumping genes” will appear in places where they affect gene expression. Here, they cause a cell and its daughter cells to be rendered unable to carry out some designated functions. However, the “jumping gene’s” occupation of a particular place in the chromosome is temporary. So, the interference with genetic expression is likewise. 

How it Works

In the event that a “jumping gene” is present and it interferes with the gene that is responsible for producing black (melano) pigmentation, it can stop the production of black (melano). In that case, all the progeny cells (a clone of cells) will also not be capable of producing black (melano). That causes a non-black patch to appear on the fish, manifesting itself as cellophane or white area.

And the reverse sometimes happens too! The “jumping gene” can inhibit black (melano) creation, then leave. Afterward, the progeny of that cell (a clone of cells) will be capable of producing black (melano) again (reverts). As a result, a patch of black (melano) will appear.

Occasionally, a dark patch that manifests itself on a light-colored marble fish develops a light spot in the center, appearing rather like a bullseye. Imagine a clone of growing cells that cannot initially produce black (melano) because of the inserted “jumping gene” (the pale background of the fish). 

When the “jumping gene” leaves the compromised melanin-producing gene in the growing fish, melano production resumes, creating a dark patch. Later in the fish’s growth, the “jumping gene” is reinserted, affecting the melanin production of a smaller group of cells, creating an inner light spot in the dark patch.

How it Relates to Marbling

So, the theory of the “jumping gene” also goes some way to explaining why some marble bettas never marble. 

If the “jumping gene” fails to insert, as in the case of a dark-bodied fish, or leave, as in the case of a light-bodied fish, in any of the fish’s cells during the growth period or life of that fish, then marbling will simply not occur.

That could also work with other pigments, i.e., the capability to produce blue, green, steel blue, and red pigments. The “jumping genes” could insert themselves into the genes that are responsible for creating those pigments, turning on or off the pigment-producing capability of groups of growing cells in the maturing fish. 

Final thoughts

There is a lot of evidence to suggest that transposable genetic elements, or “jumping genes” could be responsible for the marbling effect in betta fish. The inheritance of marbling can be explained by this theory. However, proving that could be tricky. 

However, one thing is certain, regardless of whether you are interested in the genetics of marble bettas and whatever the instrument of inheritance may be, marble betta fish are undoubtedly beautiful. And all betta enthusiasts can enjoy that!

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