Re: Borelli Thesis

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

Hi gang! I'm very glad that many of you have interest for this. I am
almost certainly going to try to publish my findings. I may even wite up a
general review for an aquarium magazine (e.g. Tropical Fish Hobbyist).
Yeah Travis, I was advised by my supervisor to test for interactions.
ANOVA sounds good. Mike, I will be maintaining the conditions constant in
the rearing tanks, from the time that they are placed into them. I am
spawning them all at pH of 6.6, and a temp of 80 F. I have been removing
the eggs the first day that I see them. According to Romer and Beisenherz,
they found that another Apistogramma species (trifasciatus? the paper is
downstairs) gave a sex ratio as predicted by the rearing conditions for
fry that were moved within 72 hrs of hatching, and sex ratios as per
spawning conditions when removed after 800 hrs. Intermediated time of
removal (between 72 hrs and 800 hrs) gave proportional effects according
to time of removal. I think that I am fine with my procedure, although it
is a different species. I think that they used acidic pH because they
believed that pH variation exists throughout their natural range. However,
they did not find this, although a temperature range was found with
respect to depth of the river. The temperature range was very small, and
didn't satisfactorily (my opinion) explain the adaptive significance of
environmental sex determination. I have a good idea, and it will link
their perculiar behaviour with environmental sex determination, but I'll
leave you in suspense for now because it's part of my original thesis. 

Cheers,
Jonathan

-------------------------------------------
Jonathan Fung... Reef Geek
Dalhousie University Honours Marine Biology
Aqua Creations Inc. Assistant Manager
writer for Marine Fish Monthly 
-------------------------------------------
email: fung@is2.dal.ca




On Thu, 14 Dec 2000, Travis Dahl KE4VYZ wrote:

> 
> >
> >    You know, when I looked at that paper, I did notice their were some
> > temp/pH combinations that seemed underrepresented and I wondered about the
> > statistical significance too...
> >    A few thoughts:
> >    First off, I'm really jealous.  Someday I'll have enough time/space/$$ to
> > do something like this. <sigh>
> >    There may only be one or two broods per temp/pH combo, but each of those
> > broods may have been sizable...Which does leave you open for the possibility
> > of correlations within the brood (i.e. genetic predisposition based on a
> > given set of parents, etc.)
> >    Jonathon, when you get your data, I would suggest using a two-way ANOVA
> > (as probably will anyway)  to test for interaction effects (i.e.  Temperature
> > has an effect and pH has an effect, but so does the _combination_ of pH and
> > Temperature)
> >    As always (and I can say this because of my strong statistics background),
> > statistics can't actually "prove" anything, but they're about the best tool
> > we have.
> >    Sorry if this rambled a bit or anyone was brought to tears because of the
> > references to statistics. <grin>  Good luck and keep us informed of how
> > you're project's going.
> >
> >>
> >> Date: Thu, 14 Dec 2000 14:37:22 -0700
> >> From: Mike & Diane Wise <apistowise@bewellnet.com>
> >> Subject: Re: 
> >>
> >> Jonathan,
> >>
> >> I rechecked the reference and you are correct. It shows 17 spawnings. I also
> >> have their
> >> preliminary report (Römer & Beisenherz. 1995. Modifikatotrische
> >> Geschlechtsbestimmung
> >> durch Temperatur und pH-Wert bei Buntbarschen der Gattung Apistogramma in
> >> Symposiumband: Fortpflanzungsbiologie der Aquarienfische, Birgit Schmettkamp
> >> Verlag,
> >> Bornheim.). In it they used 21 spawns, or about 1500 fry, with tight
> >> controls (no
> >> spawns with losses over 10% and extremely precise controls on pH,
> >> conductivity, &
> >> temperature). I assume the reason they used acid water conditions was
> >> because apistos
> >> prefer breeding in acid water. Spawns in basic water tend to lose
> >> significant numbers
> >> of fry. The eggs are laid but they often don't hatch in large numbers. I
> >> don't know,
> >> but this may explain why they have no spawns listed for basic water
> >> conditions. None
> >> met the 90%+ survival requirement. I am not a statistician so I can't
> >> comment on that
> >> part of the paper or why they considered the number of broods sufficient for
> >> statistical studies.
> >>
> >> I, for one, would be very interested in learning your results. Will you be
> >> maintaining
> >> consistent conditions from spawning to sexing? If Römer & Beisenherz are
> >> correct, any
> >> changes in conditions will change the final results. Please, let me know
> >> your findings
> >> when you finish your thesis. They will be valuable evidence to confirm or
> >> deny Römer &
> >> Beisenherz's studies.
> >
> 
> 
> 
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