Re: pH sexratio Pelvicachromis

[jonathan <fung@is2.dal.ca>]

Sorry Mike, you are right. Specific species and their distributions might
involve other pH ranges in the remote corners of the watershed. I think
what I was trying to convey is that since Rubin found pH to affect sex in
developing A. borellii throughout 6.2 to 7.2, it seems that Romer's 4.5,
5.5, and 6.5 are not thoroughly investigating the spectrum but rather the
acidic extreme of the speectrum specific to A. borellii.

-------------------------------------------
Jonathan Fung... Reef Geek
Dalhousie University Honours Marine Biology
Aqua Creations Inc. Assistant Manager
writer for Marine Fish Monthly 
-------------------------------------------




On Tue, 27 Feb 2001, 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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> > > >
> > >
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> > 
> > 
> > 
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> 
> 



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