can fish in a single sexed environment spontaniously change sex?

rhsbomberae16

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Jan 31, 2004
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hey ive got three male green tgr barbs all of which are elegedly male but it seems that the fish are breeding! and i have two male gouramies...now i have one male gourami and one female ...however they both started as males until one descided to changes its fins and coloration then laid eggs! its very interesting how can they change sex is it because all of there species in the tank were of the same gender? or am i just crzy
 
Frogs do it. I don't see a reason why fish can't.
That doesn't mean I've seen it or think it's possible, I just haven't heard otherwise. It's possible the presence of a male just brought out the colors and behavior in the female though; that's actually more likely I think. For example, our fish distributor only ships us male guppies. I have yet to see a male shorten his fins and have babies with another.
 
only some fish can do it. im sure most if not all livebearers don't.
 
This is a very common Phenomenon with Swordtails, Don't know about other breeds but it certainly wouldn't surprise me if it happened. Nature always find a way.
 
i have heard swordtails are pretty much the only ones to do this -
gourami's can be tough to sex sometimes even when you are looking at the shape of their dorsal fins - i have never heard of gouramis having the capability to change sex - i do not think it is possible - lots of times when they are new to a tank they won't show coloration - when they get settle down sex distinguishing coloration will start to show - until then you can't see much between m-f - one of my gourami's didnt show coloration till he was in my tank for 3 mos - most of the time if you check them in the lfs tanks they are somewhat nervous n won't show much color- you had a male and female all along they are now just showing their colors - there's no way you have 3 types of fish in your tank all changing sex at the same time - otherwise you woul have a scientific marvel occuring in your tank and scientists woul be flocking to collect your fish for investigation ! :)
 
More likely you have juvenile fish that have not fully developed the adult coloration and features on purchase. With many fish, the gender is difficult to determine until the fish are 6 months of more old--and few LFS sell fish that old. I don't think gouramies change gender, and I doubt barbs do. More likely, they were incorrectly gendered at an undifferentiated age. Livebearers will change sex--swordtails are well known for females developing male coloration and finnage, though the jury is still out on these fish reproducing.

Gender change in amphibians is well documented, and the normal life cycle for many marine fish.
 
OrionGirl's is right about the juvenile thing. I have also read information about most all common livebearers (molly, platy, sword, guppy) changing sex due to one thing or another. I have heard of guppies changing sex due to lack of the opposite sex in the tank. I haven't ever had it happen (that I know of) in my tanks, though. I've always had a good mix of male/female.
 
AFAIK, the swordtails do change sex from female to male if so required by the environment (lack of male). Back then my biology teacher knew quite alot of these stuffs. He had a big bowl of red swordtails (probably at like 100inch of fish per gallon or something), that he had kept for a few generations of the fish. And he has seen this happens.
 
I have a male swordtail that used to be a female. The females were seperated from the male for a few months and the female very slowly made the change, the sword had not grown as long as the born male's has but this one is trying to mate with the other female. I do not know if it will be successful though.
 
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