Quick question about hybrid fry

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pelleeklund

pelleeklund

Peacock Bass
MFK Member
May 23, 2009
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Pennsylvania
Are all of male hybrid fry infertile? Some guy at my fish store thinks so. He seems to think one of the females would have to be crossed back with another male of the parents species to have a batch of fry where both sexes can reproduce. Seems complicated but Im no biologist, and I guess it could work somehow like our own chromosomes in dictating sexual organs. I didn't argue with him or anything, to be honest I was just trying to get out of there, but I did leave thinking about whether there was any validity to what he was saying. No better place to ask than here I guess.
 
I hate to ask you such an odd question but if you had to put a percentage on their fertility, what do you think it would be? For instance maybe 70% fertility in females, 40% males? Or if that question involves too much guessing, could you tell me any more specifics about how this happens? Im guessing that they are close enough to reproduce but not so perfectly matched according to assigning their specific reproductive systems. If that's the case it's pretty interesting that they can actually reproduce at all, just getting enough of the wires right to make a fish, not necessarily a complete fully functioning fish. Thanks for the reply too buddy.
 
It all depends on what type of fish your breeding. Just do some research on the fish you plan on breeding together. But for example a Texas x Convicts Id say most if not all will be fertile. Now if you breed the texas x con to a midas Id still say the fry will be all fertile. But a male Flowerhorn zz bred with a female vieja , some males will be infertile but all females should be fertile.
 
It varies between crossbreeds.

What happens during any sort of breeding, is that each parent donates a set of chromosomes to the child. In closely related parents (i.e. individuals of a species), the chromosomes align pretty much perfectly.

In interspecies breeding, you can imagine that of course the parents will have very different genomes, and so when you crossbreed you'll get two (possibly very) different sets of chromosomes aligning together. It's all up to chance, and how well the two sets happen to align.

In most cases there will be sections of one set that does not align at all to the other set, and vice versa.

Basically this, imagine one set is ABCDEFGH, whilst the other is ABCGH. Obviously there's a huge chunk in the former set that is not present in the latter set, and what occurs depends on what genes this section represents specifically.

Especially for sex chromosomes, this have a huge effect as a male relies heavily on its Y (or the equivalent in fish) chromosome working, and so just a small discordance and the function would be completely off, rendering the male infertile. In the female it has XX (or the equivalent), so even though it's two different X from two different species, if anythig does go wrong for one X there is a higher chance that fertility is 'rescued' by the other X.

Back-crossing 'saves' sterility because of this:

So say one species is T, the other is H. Let's call the female sex chromosomes of the offspring XT/XH. And let the father be the H and the mother be the T.

When you backcross the offspring to the father, there's a chance of maintaining the XH and also obtaining a XH or YH fromthe father, and the XH/XH or XH/YH offspring will have (almost) perfectly aligned chromosomes, as these chromosomes now are 'from the same species'. Same with the opposite backcross.

Hence that's why sterility can be 'saved' by backcrossing.

Sorry if that didn't make too much sense, writing on phone whilst Im really hungry. >.<" But yeah, more or less as above.
 
The probably of obtaining sterility varies, but it does correlate a lil' bit with how distanced the species are from each other. More distantly related species will mean that the chromosomal sets are less likely to align (at all), which is also why certain hybrids are just not possible. XD

But again, it's up to chance. Even if two genomes are highly varied, they may still somehow align and produce young.

Also some 'closely' related species are actually genetically different enough for hybridization to not occur/be hard to occur. All species evolve at different rates, and so sometimes you have a case where individuals of two genera can't hybridize (like say Green Texans and Discus (at least there's no evidence that I've found)), but Green Texans can hybridize with Mayans (different tribe). So yeah. :P

So yeah, really cannot tell overall the chances of sterility. Though the probabilities for some of the more well known hybrids are estimated, I think. Chris can correct me here (I don't know that much about Blood Parrots) but I believe in Blood Parrots there's about a 95% chance that the males are sterile and a 5% chance that the female is sterile.

Also if you think about it, the guy at your lfs contradicted himself. He says that all male hybrid fries are sterile, then went on to say that hybridizing a hybrid with one of the parents will produce viable male fry. Mating a hybrid with one of the parents will obviously produce a hybrid, so obviously at least some male hybrids are fertile, which means that not all male hybrids are sterile. XD
 
I love it, you guys know your stuff. Thank you for taking the time to help me out. Ironically this whole conversation started when the guy was asking me why I was buying a divider. Rather than telling him it was because the one I rigged up was a miserable p.o.s., I just mentioned that my jag and con had bred and I wanted to set up a decent area for fry to be safe if necessary. In the interest of maintaining polite conversation through the checking out process I joked that I was nervous having so much convict dna in one tank. I'm not, but it just crapped out. He mentioned that I wouldn't have to worry because the males are all going to be sterile etc, your safe from an infestation. It was just a short jokey conversation that stuck with me as I drove home. I guess your living the dream when your driving around and the only thing that's bothering you is why hybrids would become infertile. Azedenkae thanks again for the details, really appreciate your time. Matt thanks too bud. Also on a side note, the divider is nice, it's pretty streamline and even though it's about 17 bucks, aesthetically it's tight and I can appreciate that. My Pvc, paint strainer, zip tie contraption was fugly and sort of floated. Short sighted on my part.
 
First batch disappeared after I moved the mother to the other side of my divider. Then I noticed the design flaws. They basically could swim right over the other side. Can't say for sure what happened but they look like they are getting after it again though so I'm sure I'll see more soon.
 
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