Lake Malawi Species • Black Zebras???

[drewsda45]

My ob zebras have been producing a few all black fry for the past few spawning. Has anyone seen this before? The pic is of two smaller ones but they retain the full black coloring as they grow.

[Deeda]

Do you have pics of the adults?

Any other cichlids in the tank with them?

[sir_keith]

Do you have pics of the adults? Any other cichlids in the tank with them?

Exactly. The $64K question right now is who are the parents of these little guys. And what do you mean by 'a few,' percentage-wise. And these fry are viable, and grow into all-black adults? I've not seen this before, and it's really interesting.

[drewsda45]

The only other mbuna are
Albino red top hongi
Yellow labs
Also some sciaenochromis fryeri, one tropheus duboisi
The rest are South American.

There are several very heavily black spotted orange (very little orange at all)obs in each batch of fry, but only two or three of the solid black ones. The biggest one so far is about an inch and is still black.

[drewsda45]

This is the male. The female is a regular orange with black spots
OB zebra (in the background).

[drewsda45]

I forgot that there are also tomato haps in there. Nothing seems like it would produce black fry hybrids. Also when the obs are spawning the male is crazy aggressive and drives everyone away from the female.

[sir_keith]

Well, given the inhabitants of your tank, I would say that it is very likely that the two fishes in the pic you posted are the true parents. So what to make of the black progeny?

OB Malawian fishes differ dramatically in appearance one from another: some have lots of black patches (like your male), some have very few (like your female). The patterns themselves are thought to arise from differential migration of melanocyte precursor cells (black pigment-producing cells) during development, and clonal expansion of their progeny. For example, if you look at the male's tail, it is easy to imagine that whilst this embryo was developing, between 6-8 melanocyte precursor cells were located in the tail bud (at the base of the tail), and as the tail grew, each of these precursors gave rise to the melanocytes that occupy each of the 6-8 'rays' of black pigment in the adult tail. The same is true throughout the body of the fish. The point here is that the pattern is unpredictable, because it depends on the migration of individual melanocyte precursor cells during development. That is, the pattern has a somatic, not a genetic basis.

Given that unpredictability, the surprising thing is that your little black fishes are so black, without light patches anywhere. One way to explain this would be to say that these particular embryos had an excess of melanocyte precursors, so that pigment-producing cells came to reside virtually everywhere in the body, producing all-black fishes. This would be consistent with your observation that you also obtain very heavily black-spotted OB fry.

I would encourage you to keep as many of these black fishes as you can, and when they mature, to cross them to each other. In the next generation I would expect many all black progeny, but at some point OB fishes may reappear in the pedigree as well.

This is cool; keep us posted!

[drewsda45]

Thanks for the detailed information about how the pigmentation works in OBs. I was planning on crossing the blackest fry after they grow out. It truly will be interesting to see what I get.

[sir_keith]

Thanks for the detailed information about how the pigmentation works in OBs. I was planning on crossing the blackest fry after they grow out. It truly will be interesting to see what I get.

I agree, and like I said- keep us posted. I'm thinking that these could grow up to be very pretty fishes.

[noki]

Seems like you have a parent combo that is producing another level of mutation, very interesting. Raise both the all black and some orange black fry, and see if the all black has both sexes or whether they are just one sex. You may have to breed an all black one with their OB sibling to try to get more black fry. Share some pics when they get bigger!

[sir_keith]

Seems like you have a parent combo that is producing another level of mutation, very interesting. Raise both the all black and some orange black fry, and see if the all black has both sexes or whether they are just one sex. You may have to breed an all black one with their OB sibling to try to get more black fry. Share some pics when they get bigger!

That's a good point. For sure the plan going forward would be different if all the black fry are one sex, in which case crosses to their OB sibs would be the next step.

[drewsda45]

Good point. I never thought about the black ones potentially being one sex. I'll post more pics as they grow. They'll be difficult to sex so if anyone has ideas for help with that I'd welcome them. I haven't developed a keen enough eye for venting fish.

[noki]

Good point. I never thought about the black ones potentially being one sex. I'll post more pics as they grow. They'll be difficult to sex so if anyone has ideas for help with that I'd welcome them. I haven't developed a keen enough eye for venting fish.

Zebras get sexually mature when they get over 2.5", and males look and act like males, females stay the same. If you keep juveniles only in a tank, a few young males act dominant early in the group. Venting juveniles is not easy, so don't worry about that.

[Fogelhund]

Are they blind? For whatever reason, many cichlids turn black, when they are blind.

[drewsda45]

I don't think do. They don't behave like they're blind.