jellybean brevis

[Rod]

Anyone understand genetics???
I found a lone male brevis (kavala) in a shop I don't normally visit......he had very good colour and strong markings so I bought him....now I've got him home I see he is slightly shorter in the body the the other I have (6 pair) . I understand the gene that creates fish that are shorter in the body is recessive
so if I breed him to one of my normal females (from other pairs)... all offspring will have normal bodies....but may carry the short body gene....so If I select the best coloured male and continue to breed with normal females from my other spawns...... I shouldn't get any shortbody fry?

I'd really like to get offspring with his strong markings and colour.......with proper proportions in the body

Please Note.....L Brevis are no longer a legal import in Australia and most available are inbreed (as opposed to carefully line breed) thats why I've collected 6 pair from different sources.....to get a better mix of genetics....

 

[Mark Showell]

Your breeding plan to outsource the gene pool is a good one!

We'll assume the short body is genetic, as and not due to crowding and/or poor diet.

If it's a simple recessive gene, all the offspring (F1) from the first crossing for certain will carry one copy of the short gene (s), and one normal copy (n). If you breed these offspring, 25% will be nn (normal, not carrier), 25% will be ss (short), and 50% will be ns (normal carrier).

The colour genes are probably not simple (ie at least two & possibly several). However as an example, let's assume they are and follow a similar pattern to that above and the we have a gene which is either c (drab) or C (colourful). On the F1 cross you would also have offspring that were 25% cc (drab, not carrier), 50% cC (drab, carrier) and 25% CC (colourful, carrier).

Combining these two scenarios you will end up with (take a breath)

13/16 fish will be either shot or drab. Get rid of all those.
3/16 will be long and colourful. Of these 3, only one will be the one you're looking for (ie pure long and colourful) - you won't be able to tell which one without another round of careful breeding to 'fix' both features together. Of course, you'll need way more than 16 fry in total to get started, plus several tanks and careful note taking.

It's a big job, but possible - good luck! Mark.