Jump to content
Chuckie

Black betta genetics

Recommended Posts

Here's my attempt at summarising what I think I know about black betta genetics.

First, some definitions:

Homozygous = has 2 copies of a gene (eg 2 copies of black lace, 2 copies of melano)

Heterozygous = has only 1 copy of a gene

Recessive/dominant = if a gene is recessive the presence of the gene won't be apparent from the creature's physical appearance unless it has 2 genes for that feature. It will be 'masked' if the creature has a different gene for the same feature which is dominant. Example: I have a recessive blue eyed gene and so does my husband. We are therefore heterozygous for blue eyes. We are also heterozygous for brown eyes. We actually have brown eyes as the gene for brown eyes is dominant and 'masks' the gene for blue eyes, but out daughter has blue eyes as she got a gene for blue eyes from each of us, ie she is homozygous for blue eyes ... (yes I know the gene for eye colour isn't really that simple IRL but it is a good example, IMO).

Ok, here's what's been said on the topic before:

I also want to know what I'd get if I crossed a black orchid with a melano.

I am told that you can get light bodied fish, because the offspring won't have 2 pairs of either type of gene for spreading the distribution of melanin in the fish. If I understand correctly, you need 2 x melano genes or 2 x black lace genes to spread the black in a fish, and as the offspring of melano and black lace don't have 2 pairs of either (unless they also have a recessive melano or black lace gene), they won't be black.

So far I think I get that - but what colour will the offspring be?

And If I did a F1 cross of a melano x black lace, could I then get a black fish?

Lilli, if the black orchid is the same kind of black as black lace, and neither parent carries the other black, you would expect F1 to be normal iridescents. Their iridescence would follow the genetics of the combination of irid on the parents. If the parents carry red, this may appear. You would get real lightbodies if both parents carry the genes for lightbody. Basically, if you know what the non-black traits involved are and in what combinations, the fry produced will have those new combinations of traits.

In F2, if my punnett square was correct, only 1/16 of the fry will be double black.

The rest will either not carry black at all, or have 1 copy of 1 black; 2 copies of 1 but not the other; 1 copy of both blacks; etc. Too many combinations to say. 9/16 will not show black at all.

So to summarise what I think I know: black lace and melano are both recessive, so any fish that is black is either melano (ie definitely has 2 pairs of the melano gene) or is a black lace (definitely has 2 pairs of the black lace gene).

If you cross black lace x black lace both parents will contribute a black lace gene and the offspring will all be black lace. Easy! (Unless I missed something obvious).

If you cross melano x melano .... the embryos will die, due to a protein reaction that occurs after fertilisation which is understood to be related to the way certain proteins clump together in a melano - which is what causes the denseness of the black but also is fatal to the embryo.

If you cross a black lace fish with a melano fish, the black lace will contribute a single black lace gene. The melano fish will contribute a single melano gene. So the offspring will have only 1 black lace gene and only 1 melano gene. Because they do not have 2 of either gene for black, the fry will not be black. Weird, hey?

So what is double black? As best I understand it, it is a fish that is homozygous for black lace (ie both parents gave it a black lace gene, so it has 2 of them) and it is also homozygous for melano (ie both parents gave it a melano gene, so it has 2 of them). It looks black, and the females are fertile for some reason I am sure I'll understand one day.

SO how do you produce more melano fish if the melano females are 'infertile' and crossing a melano with a black lace doesn't give you black fish?

You can cross a melano male with a blue fish (usually steel as it is the least iridescent blue) or black lace fish. All the offspring will inherit 1 melano gene from the melano father. You then do a F1 cross, or preferably cross a female from F1 back to the melano father. We know that she has at least one melano gene as her father is melano. This will result in 50% melano offspring and 50% that are not black but carry the recessive melano gene.

OR you can use a blue/black lace female you know is melano geno (ie has 1 melano gene from her father) who is not necessarily related to the melano male. Again, you'd obtain 50% melano offspring.

How do you get double blacks? Geez, now that's getting difficult. Ok, this is how I think it works. Black lace and melano are not mutually exclusive. You can have genes for both types of black in the same fish. So Melano x Black Lace gives you offspring with one melano gene and one black lace gene. Cross 2 of those offspring and you'll get:

25% homozygous for black lace

25% homozygous for non-black (not black phenotype)

50% heterozygous for black lace (not black phenotype)

AND

25% homozygous for melano

25% homozygous non-black (not black phenotype)

50% heterozygous for melano. (not black phenotype)

So which ones do you breed to get double blacks? well ... I suppose you try a melano (denser black) pair and if the embryos survive, you know the female is heterozygous for both both black lace and melano. I can't see how there's a more reliable way, as I don't believe you could tell from a phenotypically black fish if it was also homozygous for black lace.

Maybe someone has an idea? My dinner's ready, LOL!

Share this post


Link to post
Share on other sites

so for those fish who are not homozygous to either melano or black lace. what would they look like?

if they are only heterozygous for 1 gene of each then what would thier phenotype appear to be?

and how do i find out what sort of black gene my black orchid belongs to? she has no transperant or translucint finnage so i must guess that she is a melano, right?

Share this post


Link to post
Share on other sites

Great post, Lisa :confused:

With the percentages you got, what punnet square did you use? Dihybrid? I count a 1:1:2:1:1:2 ratio so did you actually get 2:2:4:2:2:4 = 16 squares?

Share this post


Link to post
Share on other sites

Thanks Stefan, please clarify anything I may have stuffed up.

those fish who are not homozygous to either melano or black lace. what would they look like?

As per the original quote from Stefan, whatever iridescent blue they carry, and if they have red wash, red wash too. If they have 2 genes for light body then they may also be light bodied.

With the percentages you got, what punnet square did you use?

I did one using Mm (M = non-melano, m = melano - I made the codes up just for the purposes of the calculation) and one using Bb (B = non-black lace, b = black lace). I haven't got the aptitude for a punnett square that deals with more than 4 alleles :confused:

how do i find out what sort of black gene my black orchid belongs to
unless I am mistaken, black orchid = black lace. If you spawn her and the embryos survive, you'll know that for certain. (Unless she's double black, which as you know, is not highly probable!)

Share this post


Link to post
Share on other sites

In regards to your percentages then, that cross (heterozygous for both blacks x same) should also produce fish that are homozygous for both blacks (double black), and fish that are homozygous for one black but heterozygous for the other black. You can't see this if you deal with the 2 pairs of alleles in separate (monohybrid) punnett squares :( . I will post a dihybrid punnett square with all the details and percentages for this cross tomorrow :D .

Share this post


Link to post
Share on other sites

Punnett Square for heterozygous melano and black lace x same:

Key: Letters symbolise a gene version (allele). Uppercase for dominant allele for a gene, and the same letter in lowercase for the recessive allele of the same gene.

M = non-melano

m = melano

B = non-black lace

b = black lace

Double black = mmbb

Punnett Square

MmBb x MmBb

MB Mb mB mb

MB MMBB MMBb MmBB MmBb

Mb MMBb MMbb MmBb Mmbb

mB MmBB MmBb mmBB mmBb

mb MmBb Mmbb mmBb mmbb

Genotype Frequencies:

MMBB: 1 ( 6.25% )

MMBb: 2 ( 12.5% )

MMbb: 1 ( 6.25% )

MmBB: 2 ( 12.5% )

MmBb: 4 ( 25% )

Mmbb: 2 ( 12.5% )

mmBB: 1 ( 6.25% )

mmBb: 2 ( 12.5% )

mmbb: 1 ( 6.25% )

:)

Edited by splendidbetta

Share this post


Link to post
Share on other sites

I was told at the LFS that a large percentage of black bettas get tumors due to the amount of melanin in their make up. Is this true?

Share this post


Link to post
Share on other sites

She was definitely talking about tumors. If her line of reasoning was true, surely you would see this problem in other black coloured fish. I didn't really believe it, just thought I'd get some clarification...

Share this post


Link to post
Share on other sites

I haven't seen any incidence of tumours in black bettas. It is something to watch out for in black mollies though.

Trade names often confuse the issue.

This pair were shipped as "Super Black" Genetically I would refer to them as "double black" mmbb Quite intense black on the female.

Steel and blue females from Melano lines have a black checking (like a hounds tooth pattern) through the fins.

If desired you can also cross a melano male with black copper females to produce a gold and black bi-colour. There were some stunners of these around a few years back.

Cheers, J

Share this post


Link to post
Share on other sites

I'm sorry for my ignorance but could someone please tell me what a super black is? Is it likely to be infertile? I'm looking at bidding on a giant super black to help with a dark purple pair that i am looking at buying but don't want to if it's likely that he's going to be infertile.

Share this post


Link to post
Share on other sites

From Betty Splendens:

Super Black: This is a loose terminology. It can refer to black bettas that come from metallic/melano crosses and therefore appear darker than typical melanos, and it's also tossed around to solid, marble-based dark-dark-blacks that may also carry melano. They can be shown in the Black class.

Share this post


Link to post
Share on other sites

People seem to be using the term to refer to fish that are homozygous for both black gene and melano gene. Therefore sometimes called double black.

It's melano FEMALES that have fertility issues. They produce eggs, but they fail to hatch. Males are fertile.

Share this post


Link to post
Share on other sites

Bump!

As Maddie is working on Black Lace, and I have a black CTPK line in the making, I thought it might be useful to bring this post back into the light of day. It is also a reminder of what a wonderful group of people we have had, and continue to have involved in this forum.

Maddie - if I read this right, that being black orchid = black lace (as in the black gene required to make the black part of a black orchid is the black lace gene), and black lace also comes from some marble crosses, then my black orchid CT x black marble HMPK cross should produce geno black lace combtails, and a sibling cross could produce a percentage of black lace CTPK in F2... :D

Edited by Brenton

Share this post


Link to post
Share on other sites

Brenton, you are forgetting that your female is a marble. You have the possibility of getting cellophane, marble, blue (type depending on the type each parent is carrying) and possibly even red wash (though a lot of marble lines you get red loss - one of the reasons it is so hard to find solid blues that don't carry marble. Breeders used marbles early on to reduce red wash in their solid blue lines.) not saying that you won't get any solid black, just prepare to expect the unexpected with your spawn. Most of the siblings to the marble girl you have didn't start marbling until at least 3 - 4 months, so keep that in mind if your fry look solid when you start jarring them.

Another interesting thing to note (and I'll have to do a little searching to find the source), is that I have read that you can get fertile melano females. The trade off is that they always have a high level of blue iridescence on the body.

Share this post


Link to post
Share on other sites

Cheers Jarrod - am I right in thinking all you say is a possibility in F1, but being selective for my F2 cross would look to narrow those odds, or as all my F1 will inherit the marble gene from the mum, that these possibilities will continue regardless into F2?

Yep - I have three other HMPK girls from Leah, two of which only started to marble to black a couple of weeks ago (they look almost piebald now). The third was always an interesting mix of blues (mainly steel, I think). But yes - with marble on the table, I'm keeping my expectations low and my interests high, but blacks are the goal for this line as we move along.

I've also read that melano females can be fertile, but it's rare. I think these are the ones that are based on steel as well...not sure, need to reread about blacks and do lots more research. Any sources you can point me to would be appreciated.

Share this post


Link to post
Share on other sites

It is almost as hard to remove marble from a line as it is with red wash. You never know when it will rear its head...lol. Through selective breeding you will at least get some solids each generation.

  • Like 1

Share this post


Link to post
Share on other sites

×