sex?

[evofish]

at what age can you determin the sex of guppy fry?mine are about 4 weeks and they all look females its weird they have an anal fin and no gonopodium

 

[MissD]

Apparently it's about 6 weeks...I have some 4 week and some 1 and 2 day old fry, and all of the older ones look female too.

 

[evofish]

so do there anal fin change in gonopodium?

 

[paulthegreat]

Livebearers tend to have a sex determination when they are about 60-80% full grown. How fast they develop can depend on a lot of factors, feed, temp, water conditions, maybe even pH and crowding factors can play a roll. Genetics can also play a part in this development. At four weeks I would guess that they have a bit to go before they start to convert to male form. I have Swordie juvies that are about three to four months old and a few are starting to show the anal fin/gonopodium transformation. Guppies may go a bit faster.

 

[mlee0332]

so in a way they are "sexless" and then they change into a male or female??? I have 1 day old fry and they look female as well.

 

[paulthegreat]

They are born all female and then a number of the fry convert to male as far as I have been able to come to. Have you seen Jurassic Park? This can happen in amphibians and fish that the population of a certain spiecies will adapt to see too that there is a genetic balance to ensure propagation. At least that is the way I understand it.

 

[SnowyzMom]

Really I just thought the male guppy fry were keeping their fins tucked between their legs so to speak so they could get to stay in the female guppy tank longer! I check that tank daily and suddenly BINGO, there's a male where the day before they were all females. Sneaky or what?