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RE: Sex change in Apistos???

As far as I know, Apistos do not use chromosomes for sex determination.  Sex is determined by temperature, which is thought to influence the levels of sex-determining hormones.  The evolution of sex chromosomes is related to internal gestation (ie live-birthing), so all placental mammals and some reptiles.  I'm not sure how fish like Gambusia achieve their sex ratios, but it may have to do with them being unable to regulate their body temperature like live-bearing reptiles can, so they too are at the mercy of the water temperature.

As someone else mentioned, sex changing at maturity is not an uncommon phenomena in fish, especially saltwater fish.


> -----Original Message-----
> From: owner-apisto@v2.listbox.com 
> [mailto:owner-apisto@v2.listbox.com]On
> Behalf Of Archie Christian
> Sent: Wednesday, 5 May 2004 04:22
> To: apisto@v2.listbox.com
> Subject: RE: Sex change in Apistos???
> Forgive my limited knowledge of fish genetics, but if there 
> is a change
> in sex and successful spawns, is the genetic information passed on the
> same way everytime, or does it change?  ( I am thinking of X and Y
> chromosomes)...will the once female-now male produce Y
> chromosome-related genetic material to pass to the fry? or has anyone
> noticed or documented spawns of only female fry in these cases?  Does
> sex-linked genetic material exist in fish?  it seems someone opened a
> whole can of blackworms...

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