Re: pH sexratio Pelvicachromis

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

Jonathan,

I'd be interested in seeing your references. I can list dozens of references that show pH in
the wild at  lower values. Many show variable values at the same location at various times of
the year, but all are acidic (most are always below pH 6.5). The Amazon Basin is a big place.
Unless you are in a whitewater or certain clearwater areas, pH values are more often below pH 6
than above. After all, even natural rainwater has a pH below 6 as it falls to earth. I assume
that since low pH values are what the species are adapted to, thos why we have to uses the low
values to successfully breed them.

Regarding growth, there is a lot we don't know about its effects on fish. I agree, it's
something for some other eager young ichthyologists to investigate. Any takers?? :-) Still I
eagerly await the results of your thesis. Please keep us informed.

Mike Wise

jonathan wrote:

> Studies on the Amazon watershed indicate that the seasonal pH regime
> fluctuates between 6 to 7.2. Thus, 4.5, 5.5, and 6.5 falls on the acidic
> extreme of the pH variation spectrum found in natural annual pH regimes.
>
> Growth and development (specifically mitosis rates) are affected, even
> while raising fry. At 82 F, eggs hatch after 2 days, at 72 F, eggs hatch
> after 5 days. The window of sensitivity appears to be between 72hrs and
> 800 hrs. I was implying growth as synonymous with development, my bad.
>
> Your suggestion sounds interesting, but I am only doing one thesis and
> the deadline is approaching. Someone else might wish to try.
>
> -------------------------------------------
> Jonathan Fung... Reef Geek
> Dalhousie University Honours Marine Biology
> Aqua Creations Inc. Assistant Manager
> writer for Marine Fish Monthly
> -------------------------------------------
>
> On Tue, 27 Feb 2001, Mike & Diane Wise wrote:
>
> > 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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