Re: pH sexratio Pelvicachromis

[Mike & Diane Wise <apistowise@bewellnet.com>]

Jonathan,

Your use of the term "acidic extremes" bothers me. What pH values are "extreme" actually
depends on the species being bred. There are many species that find pH 5.5 (e.g. A.
paucisquamis) and even 4.5 (e.g. A. sp. Weißsaum) not only acceptable, but necessary for
successful reproduction. Neutral to slightly alkaline conditions don't just produce
unsuccessful spawns, but even the adults have problems surviving in them.

You will also note that Römer & Beisenherz claim that spawning temperatures are not the
primary sex determinant. It is the temperature at which the fry are raised. I imagine
that growth could play a part in this. You might be able to test this by seeing if poorly
fed fry raised at high temperatures produce the same sex ratios as well fed fry at lower
temperatures (This assumes that both groups would grow at about the same rate.). If this
could be proved, then we would see temperature being less important > for Apistogramma <
than growth rate. Pelvicachromis, however, don't seem to work the same as apistos.

Mike Wise

jonathan wrote:

> Romer and Beisenherz found that temperature has more effect than pH.
> However, they only looked at 4.5, 5.5, and 6.5 which can be considered
> acidic extremes. Furthermore, since temperature has an effect on growth
> rate, it is possible that growth rate is a confounding variable.
> Therefore, the validity of the claim is compromised.
>
> -------------------------------------------
> Jonathan Fung... Reef Geek
> Dalhousie University Honours Marine Biology
> Aqua Creations Inc. Assistant Manager
> writer for Marine Fish Monthly
> -------------------------------------------
>
> On Tue, 27 Feb 2001, Jacques BESSON wrote:
>
> > Is the influence of the pH about sexratio on the fry of this fish the same as  to
> > apisto ?
> > The study of Romer , about Apisto, concludes ( if I remember correctly)  : " Low pH
> > (5.5 and below) produced more males", and influence of temperature is more
> > significant than pH.
> > An idea about ?
> > Thanks
> > J.Besson
> >
> >
> >
> >
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