Tropical Fish Keeping - Aquarium fish care and resources

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TankMAster 05-05-2010 08:05 AM

Male+Female molly
Okay, this is a really funny story yet very interesting.

Over my period of keeping mollies I have encountered many issues that were easily solved but recently I have been arguing with myself on mollies changing gender.

Initially I purchased a few mollies knowing clearly what gender each one was. I later noticed the bigger molly (initially a female) change into a male!!!

I was doing my usual feeding a few months back when I noticed my biggest female with male parts...not only did he now have a gonopodium but still had it's female parts later became a fully finned male in a week.

Now...recently I purchased 3 mollies making sure all where pregnant....all of them genuine females. One of them jumped out of the tank and died so this leaves two. One of them has a blue shimmer and the other is a solid yellow with streaks of black.

Both these mollies gave birth when placed in my outdoor pond and brought indoors to complete their drops together. I just noticed that the molly with the shimmer has both reproductive organs :shock:

I don't know if anyone else has an explanation for this or if it's the food I'm feeding them :lol:

Did anyone else notice this?

Austin 05-06-2010 07:18 AM

Maybe it's fan fin on the female just looks a little pointed. Could be why you consider some hermaphrodites. I've had a guppy change gender and I think it happens. Not sure if it is because they mature later or what.

ferszty 05-16-2010 03:17 AM

same with one of my guppys. did u know swordtails can change from female to male.

Oldman47 05-16-2010 01:52 PM

None of the listed fish can undergo a gender change but many males especially swordtail males can be late developing their obvious external sex characteristics. They have their gender determined by X and Y chromosomes, much like people do. I kept a group of 6 Xiphophorus helleri for a period of two years. They were all juveniles and about 2 inches, 5 cm, long when I got them. All of them looked like females bu I was aware thqat swordtails can be late developers. At about a year old, one showed that it was male by starting to develop both a gonopodium and the extended tail. No fry were ever born in that tank. At about 18 months old, the next one started to show it was a male. At around 2 years old,k 18 months in my tanks, two more showed signs of being male. At 2 years in my tanks, about 2 1/2 years old, the fifth one had developed a nice sword and the last one was starting to show signs of developing both a sword and a gonopodium. I then sold them since I do not have any space to keep a single sex colony of all male swords. When I sold them, they were fabulous looking specimens at well over 3 inches, 8 cm, long. If I could have found a female, I might have been very tempted to breed them but I had no such luck.

TankMAster 08-02-2010 06:30 AM

Replies to the posts above:

This has been proven and can occur in live bearer females only! Once the female has transformed into a male, it is very unlikely that the change can be reverted.


Oldman47 08-06-2010 07:04 PM

The simple reasomnthat the "sex change" cannot be reverted is simple TankMaster. No sex change has happened. A young fish has started to show their true sex and that has confused the fish keeper, not the fish. As I already said in an earlier post in this thread, the sex of the common livebearers we keep is determined by the chromosomes of the fish, not some simple thing like tank water chemistry as happens with some cichlids. They can't turn back because they never turned in the first place. They merely allowed us to see their gender.

eileen 08-06-2010 07:34 PM

Platies are the same way. They are related to swordtails and they take along time to determine the sex. All my Bumblebee Platies look like females now. I'm sure that some of the fry will turn into males over time.i

Oldman47 08-06-2010 09:41 PM

Right you are Eileen. Platies are as likely to not reveal their true sex for a long time as swords.

kitten_penang 08-07-2010 09:34 AM

i know one fish that can change's the SW parrot fish =)

Oldman47 08-08-2010 09:24 AM

Many fish do not have the genetic fixed gender that we see in poeciliids, Kitten. Those fish are affected by simple things like a lack of one of the sexes in the tank. One or more will almost always switch to become the opposite of the sex that is already present. That is not the case with genetically determined fish like guppies, mollies, platies or swordtails. It is also not the case with the goodeid group of livebearers.

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