Tropical Fish Keeping - Aquarium fish care and resources

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dormfish 10-12-2011 03:51 AM

Livebearers: The Unusual Breeder
 
I see too many users here always asking the same old question, which is essentially: "Where did all these fry come from?" A lot of new fish-keepers are often stumped by the mysterious pregnancies and fry they find when they keep livebearers. This is a little guide to understanding the reproduction of livebearers.

There are four main livebearing species commonly kept by aquarists: Platties, guppies, mollies, and swordtails. These are very special fish, because unlike most fish, they give birth to live young. What's even more astounding, is that not only do the young develop inside the mother, they also develop without an encasing egg. They are nourished by means of an umbilical, much like humans.

Mystery Pregnancies - It's not uncommon for an owner to discover, maybe months after purchasing their fish, that it is pregnant. In the cases in which no males were with the females, you can imagine the confusion. Fear not, this is normal. In most cases, when you purchase one of the "Big Four" breeds, the odds are any female will be pregnant already, if not, carrying sperm.
Carrying sperm? Sound odd, yes, but mollies, platies, guppies and swordtails have a unique pouch inside their bodies that allows them to store sperm after mating for up to about 6-9 months. The males are also unique in the way they deliver their sperm in 'packets.' These packets are designed to be stored by the female and used whenever conditions are optimal for releasing fry. Again, not all livebearing species have this little feature, but the four mentioned above do.

The gestation period for the average livebearer is approximately a month. Towards the end of the pregnancy, you'll notice the mother 'squaring off,' which is when she will literally look square in shape from the back. The gravid spot by her anal fin will also get bigger. The gravid spot is essentially the eyes of the developing fry that you can see through the mother's scales.

Finally, it's time for the mother to drop the fry. The fry can be dropped over the course of a couple days or several hours. For the 12 hours during and after dropping the fry, the mother's body will produce a hormone that will keep her from eating, and eating the fry, but after those 12 hours, the fry will need someplace to hide, or else be eaten by other fish, including their parents.

This is all for now. More may be added later.

For more info, feel free to visit Breeding Livebearers

Groovysunflowers 10-12-2011 06:37 PM

Very cool! I basically learned everything I needed to know when I bought my first molly, unaware that they are often pregnant...now when I visit the pet store, I usually get weird looks when I specifically pick out the most pregnant looking females, lol. This is very good information, although I had no idea they have a hormone that prevents them from eating for 12 hours, that's new to me! Thanks for sharing this, I, too am getting annoyed at all the constant posts I see from people buying pregnant mollies and then not knowing what to do with them.

I was at the pet store the other day purchasing a male Molly and was tempted to ask the store owner if I could take home the fry in a couple of the tanks, I just love the babies so much, lol! I was glad to see they had the fry in seperate tanks, so I feel a little bit more comfortable about shopping at that particular lfs.

eileen 10-13-2011 10:11 PM

Free Fry at Petsmart/Petco
 
I've been to the two major chain pet stores and both will give you fry that you spot in the tanks for free. I remember seeing someone that spotted baby shrimps and she was able to get those for free as the store can not sell the babies. In most cases they get eaten by the bigger fish in the tank. All you have to do is ask them if you can have the baby fry. I've never been turned down. It may be best to ask for the free fry you see when they are not really busy with customers buying fish. But I'm sure they will help you after taking care of the paying customers.

Crocer 11-01-2011 05:37 PM

My ex- girl friends brother asked for some free cichlid fry( I know they arn't live bearers) and the pet store gave them to him as long as he bought some fish food.

thekoimaiden 11-09-2011 08:49 PM

Great post, Dormfish. I love fish reproduction. It amazes me how little the general population knows about it. Mouthbrooders, livebearers, shell-bearers; it's all fascinating to me. I've done quite a bit of research on it despite never having owned any of these fish. In fact, not all livebearers give nourishment to their young. Guppies, platies, swordtails, and mosquitofish are ovoviviparous, meaning that they just hold the eggs internally and don't nourish them. The nourishment comes only from the yolk. Many sharks also have this form of livebearing. Many species of the Goodeidae family are viviparous livebearers. These are the species that give nourishment to their young via a trophotaeniae, a structure analogous to the mammalian placenta. It pops off shortly after the fish is born. Fish reproduction and parental care is a fascinating topic; it is a topic I would love to do professional research in.


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