Inbreeding In Mollies

I have a 30 gallon tank with 4 female mollies and NO males, but that's never stopped a live-bearer, so of course I've got fry. My first batch of fry is a little over a month old and are currently counting 11. We lost one who's tail was bent, and there a 2 more, one who's tail Finn is growing with a kink in it, and one who I think I'm going to loose, when appears to have some sort of bowel malformation that has resulted in a prolapsed anus.
Is there such a thing as inbreed mollies?

 

Most livebearers are inbred to produce certain colors. I would rehome all fry until the females stop producing babies, before the fry reach an inch in size and start to develop into males and females.

 

Mollies tend to be inbred, or more often in stores... line bred. Which is kinda worse in some ways, at least to human thinking. Line breeding is you get the best looking male, then of each generation you pick the best looking females and breed them to that male. Keep the process going to get those traits. All based on a single male, and its generational off spring. Fairly common in the fish and dog worlds.

I would isolate the fry asap, and remember, they store sperm for a while so it may happen again.

 

There's a difference between inbreeding in dogs/mammals and in fish though - it's much safer in fish and doesn't result in genetic defects until generations in, whereas if you breed sibling dogs you'll almost certainly have demented puppies. I wouldn't worry about your mollies though!!

 

There's a difference between inbreeding in dogs/mammals and in fish though - it's much safer in fish and doesn't result in genetic defects until generations in, whereas if you breed sibling dogs you'll almost certainly have demented puppies. I wouldn't worry about your mollies though!!

It takes a couple generations for it to show up on them as well, seven seems to be the limit for fish, so you want to bring in new blood before that point.

 

With livebearers, "several generations" occurs very quickly. My personal experience (with guppies, not mollies) is that health problems and physical defects become noticeable after the third or fourth generation (scoliosis being the easiest one to spot). Those sure sound like inbred mollies to me. It's not the end of the world, though. You can't help who they got pregnant with before you got them, but if you do end up wanting to breed them, just remember to introduce genetic variety regularly to strengthen the line.

 

Adding genetic diversity in is a major problem home breeders have in many types of aquatic livestock. I actually just picked up 5 beautiful blue dream neocardina shrimp to hard to a new colony I setup. It's now half old bloodlines and half new.

But in general you need to bring in additional bloodlines. Honestly, at some point I may mix offspring from the two colonies to make a third adding in some more bloodlines to each along the way.

Thus may also be one of the issues with a lot of mass bred rams. I much prefer getting locally need fish though there is always that old saying. 'Wild fish want to breed'.

 

Those problems are all from environmental conditions, not from inbreeding. Inbreeding and line breeding in Mollies does not cause genetic problems unless the problem comes in with the original fish. There are many claims of inbreeding producing deformities, but 95% of these are environmental problems, not genetic.

There are some species of fish that are susceptible to genetic deformities, but certainly none of the common livebearers are included in this group. I know for certain that Swordtails can be line bred for over 50 generations without problems, it's been documented. Dr. Norton kept certain species of Mollies for many generations so that she could use offspring of that species for hybridization experiments. She developed many of the more popular color varieties available today, such as the Gold Dust. She also line bred the new varieties several generations to make sure they were stable and would continue to breed true.