Hey Lisa, Ken, Juan... real long time no see. This is my first post again after so many years away from forums. After I let my own forum, the Australian Dwarf Cichlid Discussion Forum, close down some 8-9 years ago now I have not participated in any of them. Krib are still my favourite fish and I kind of wish I had never let the Krib Project die out here in Australia... bygones... I have them again now with a bunch of fry (normal coloured Dad and albino Mum... there is a reason I do it this way too) and thought it would be good to add a few corrections here...
The information listed here so far is almost right... but not quite...
Albinism in kribensis is not dominant... it is co-dominant. This means that you will get a partial expression of albinism and
wild-type in heterozygous individuals. Albinism cannot be carried by kribensis without some degree of expression. To assist with explaining things we need to assign an arbitrary letter to each trait; 'A' for wild type and 'a' for albino (which implies it is recessive due to the lowercase letter... but it isn't... it's just a letter designation for the sake of making the explanation easy). Each individual will have two genes at the 'A' locus; one from Mum and one from Dad. Wild-type will be ‘AA’. They will look like standard wild krib. The number of ocelli is a trait that can be selected for and increased as can the intensity of the colouration of the red in males. From what I can tell/remember this is not due to pigment but flushing blood through blood vessels near the skin's surface. It is another characteristic that seems to suffer with indiscriminate breeding. Homozygous albinos will be ‘aa’. They will be true albino and not have any trace of colour on them at all. The ocelli will look translucent instead of black; in other words they will be completely void of pigment because homozygous albinism will completely mask all other colour genes (epistasis). The red colour in the eyes is actually a reflection of the blood flowing through the veins in the retina magnified through the lens. When you cross a wild-type (AA) with a true albino (aa) you will get individuals with the genotype ‘Aa’. In this instance you will get some pigment throughout the body. In my experience this is often yellow but you can get red and black as well though it will appear dilute. Black will appear grayish. You can tell these fish immediately in a bunch of albinos because they are the ones that do not completely
lack pigment. In females that are ‘aa’ (true albinos) they will still get that beautiful rosy flush on the belly region... this too is due to blood flushing through the abdominal region... and male krib LOVE it! Now, this trait behaves more or less as it should in crosses and doing so has NO effect at all on the integrity of either line (you need to follow this post up with research on modifying genes and polygenes... these are different genes that affect the level of expression of specific genes and are the ones you need to focus on when line breeding to improve characteristics such as depth of colour... it is possible by selective breeding to breed aquarium strains of pulcher
that look like pulcher
'red'. Polygenes affect things like the number and distribution of the ocelli as well).
So this is how they breed and the theoretical percentages you should get (note: these are just theoretical crosses. In actual fact it is more like tossing a coin but if you were to breed large enough numbers of them you would get close to these values):
1. Wild (AA) x wIld (AA) = 100% wild (albino is not possible unless you get a spontaneous mutation).
2. Wild (AA) x albino (aa) = 100% ‘Aa’. These will all be partially albino but will be pigmented somewhere... some can look almost albino (that's those polygenes again) so look hard. They might give themselves away with a red line along the top of the dorsal or a yellow tinge on the gill covers etc. For the sake of this explanation I'll call them heterozygotes. In this case wild-type and true albino is not possible.
3. Wild (AA) x heterozygotes (Aa) = 50% wild type & 50% heterozygotes (i.e. partial albinos. True albino (aa) is not an option).
4. Heterozygote (Aa) x heterozygote (Aa) = 25% wild type (AA), 50% heterozygotes (Aa), and 25% true albino (aa) (You get all three variants).
5. True albino (aa) x heterozygote (Aa) = 50% true albino (aa) & 50% heterozygote (Aa - i.e. partial albino. Wild-type is impossible).
6. True albino (aa) x true albino (aa) = 100% true albino (aa) (wild type or hets are not possible)
You can distinguish albino and heterozygous fry from the normal fry right from the time they emerge as they lack the peppering of pigment that wild-type do.
Case in point... in a small tank I have here today I have a wild-type male and what looks like an albino female with about 50-60 fry. There is a pretty even mix of wild-type fry and fry that lack pigment. This tells me that the female is not a true albino but is a heterozygote at the albinism locus. The wild-fry do not carry albino because this trait is always expressed in some degree... in its homozygous form it is completely epistatic of other colour genes and in its heterozygous form it is partially epistatic. Looking at my female more closely I can see she has a flush of yellow pigment in some areas giving away the fact that she is a heterozygote at the albinism locus. I know exactly how she will breed and because I like all the variants she is a good option. I also know that none of her 'white' fry will be true albinos (aa). They will all be heterozygotes (Aa) because their parents fit into option 3 above making it impossible to create ‘aa’ from ‘AA’ and ‘Aa’ parents. If I wanted true albinos I have two options. I could put one of the male fry back to his Mum (option 5 above) or cross together two of the heterozygous progeny (option 4 above – like a traditional F1 cross) and then sort out the ones that totally lack pigment to make a true breeding line. So, if your goal was to breed kribensis to improve features you should not discount using albinos or hets in the program. Their inclusion has no effect on the appearance of wild-type progeny that may result as they still possess all the other colour genes and necessary polygenes that may be useful for the program. Tthey are just being hidden by epistatic suppression of the albino gene.
Now I mentioned I like to mate albino females with wild-type males... Males are really attracted to the level of contrast of the red against the body and the red against the white stands out really well. This really turns him ON! Females prefer the wild type male colour to the albino ones… not sure why. Maybe it is an ocelli thing? Maybe it's more instinctive? When krib breed the role of the male is border patrol and defense against the dark arts... and if he dies the family is more vulnerable (though single Mums do an excellent job), and a white male is going to stand out more than the wild-type male so the female places her bet on the wild-type instead... I like this hypothesis and I usually go with this
in any case if you have both albino/het and wild males in together with a female she will most often choose the wild-type male. This stands true for albino females and wild-type females.
So that's the low down of albinism in kribensis. I was alerted to this more than 10 years ago when friend sent me a scientific article on albinism in kribensis. This paper, whose authors I don’t recall anymore, concluded the trait was co-dominant with incomplete expression in the hets. I was very interested in fish behaviour and inheritance of colour at the time because I was heading up a project call the 'Krib Project' with the goal of re-introducing colour and vigour back into mass-produced kribensis. The observations at the time were that the ocelli were controlled by polygenes and that by selecting those with the most/best ocelli you could improve this characteristic in both males and females. Seeing as we are producing aquarium strains and not breeding for conservation or possible re-introduction into the wild we can focus on superficial traits such as the number and distribution of ocelli. If we were
breeding for these reasons we would first have to determine the role of these markings and then choose the most appropriate parents to achieve the most suitable phenotype. I love to see the ocelli trait so strong in a line that even the female gets them on the tail. This is most spectacular. If you have any further questions don't hesitate to ask