Marble-based Black that Breeds True?

Since I have laid low on betta breeding over the past year, I lost most of my breeders and grow outs. However, I was left with three fish - one female and her two sons (one long-finned and a plakat/PK). The female is black. I only have a vague idea of what color the father is - a green marble HMPK. I'm not certain about that though. Because the female was able to breed successfully, then I assume she is not a Melano-based black. Eggs of Melano females do not successfully hatch - so they are effectively "infertile" in a sense (see the article The Different Types of Black for more information).

One shot of the female after spawning. Her color here suggests that it's a "Black Lace".

What's common to all three fish is that they are black. Of course, there is a fault of iridescence on the body and fins. The long-finned male started of as a black/red bicolor then changed to a butterfly pattern on the fins and marbling (white area) on the head, with no sign of red. The PK male, on the other hand, started as cellophane when it was juvenile but grew up to be solid black with no red as well. The color changes that these two fish underwent affirms that the black color is Marble-based (check this article to see how the Marble gene can change the fish's appearance). Since these fish don't show any red, they might also be carrying the Red Loss gene.

The long-finned son when he was a juvy. This fish looks like it will turn out to be a Bicolor.

The long-finned son now that he is older and has been bred.

When I crossed the Black PK male back to his mother, I wanted to get some doubletails (DT) back - whether as a DTPK or long-finned carrying PK. Given the broad dorsals of the male and his mother, there was a good chance. I did get one DT from the cross. It is black as well and still with iridescence like his father. Some siblings showed the same black color. Surprisingly, one sibling remained a Green/Red Bicolor. The number of blacks from this cross (backcross) gives a hint that the heredity of the color may be predicted accurately.

 

The Black DT.

Black siblings of the Black DT in the grow-out pond.

The Green/Red Bicolor sibling of the Black DT.

The black female was also crossed to a Copper HMPK and two Royal Blue SDs (there was a time I assumed that she is a PK). Due to the small spawn sizes, I decided to put the spawns together for efficiency. An unrelated spawn was also added to the grow out. From the mixed grow-out, I can see there are a few black fish. This hints that the black, like marble, can act in a semi-dominant manner. Most are iridescent colors and a few Marbles. (See here for more information on breeding marbles).

Black half-sibling. I think from the cross with the Royal Blue SD.

Non-Black half-sibling. Presumably from the cross with the Copper HMPK.

The next steps to check if the color does breed true is to do F2 crosses and also half-sibling crosses. The resulting offspring will provide more insight on this color. Will it breed true for another generation? Will it behave like marble - always changing color? Hopefully, I can get my hands on a Melano HMPK male and cross it to these Black fish. It will be interesting to see how this color interacts with the Melano gene. I wish that all goes well and I can write a sequel to this article.

UPDATE (Feb. 19, 2017): Pictures of other Blacks from the Black Marble SD x Black Marble SD (son x mother backcross) and Royal Blue SD x Black Marble SD (outcross).