Reptile & Amphibian Forums

Hi.
I am hoping someone can help me out. I have a gold swordtail female and a black molly male in my tank. The swordtail has given birth twice. The first time only one fry survived (she is now about six mths old) and the second time about twenty survived (they are about three mths old) The black molly is definitely the father of the second batch of fry. Many are gold with black flecks and the males bear the forked tail and lower fin of the molly rather than the swordtail that a male of that species would have. Does anyone know anything about this sort of cross breeding? None of the fish are deformed in any way and all appear healthy. I can't possibly keep all as my tank is small but I am not sure what to do with the fry.
Any advice would be great!
Thanks!

Hi.
Well I looked online because I've never had anything but guppies in a tank together. The site I looked at said the Swordtails are Xiphophorus helleri and Mollies are Poecilia sphenops. And while Xiphophorus species can cross breed, and Poecilla species can too, the likelihood of the cross breeding between different genera is unlikely. However, these fish are not in nature so I (personally) don't think the rules of nature apply. On the other hand, usually there are certain things (be that behavioral or physical) that do not allow other members of the same type of creature (for example two frog species of different genera) to breed successfully. So my answer to you is.... it could be possibly, but unlikely. Sometimes with genetics it's difficult to tell what is genetic to your female and possibly what are the genetic traits from the male's sperm. Did you recently purchase your female? If so, she could have been holding the sperm.

As for your dilemma about what to do with the fry, you can give them to your LFS for free or they may possibly do store credit... or sell/ give them away the locally.

Hope this helps.
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Phishie

"An ounce of prevention is worth a pound of cure."

I did some research as well and also found that the chances of crossbreeding were nil. But since I have the swordtail, the mollie, two catfish and an algae eater in the tank, there doesn't seem to be any explanation. I have had all the fish for over a year now. So unless she can impregnant herself(which I gather some species of fish can) or hold sperm for a long time, the Molly seems to be the culprit! Especially since she is pregnant again.
Thanks for your insight!
M

I would say it's completely possible even if the internet says it isn't then because they can't hold sperm for over a year. I guess the unthinkable is possible in your tank. As for self fertilization, that is only possible in the guppies as far as I am aware. You never really know, I guess. Your case is very special... you should feel proud of your special fishes.
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Phishie

"An ounce of prevention is worth a pound of cure."