Re:

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

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.

Mike Wise

jonathan wrote:

> Thank you Mike. I have the paper by Romer and Beisenherz. Their pH
> extremes 4.5 and 6.5 are still quite acidic. In those extremes, they also
> only used very few clutches, which was statisitically meaningless, since
> n= # of brood. Romer and Beisenherz apparently relied on work by Rubin to
> say that pH has an effect. Upon reading Rubin's paper, he only used
> one clutch per condition, at only two pH values. Basically, Romer and
> Beisenherz showed an effect of temperature, Rubin showed a very likely
> difference by pH. However, Romer and Beisenherz failed to show a
> relationship between pH and sex ratio because 1) no replicates 2) acidic
> pH used only. Rubin failed to show a relationship between pH and sex
> ratio because 1) he only used one brood per condition 2) only two
> conditions were used (intermediate values are needed to show a trend). 3)
> no replicates. These papers are useful, and that they probably are right,
> but they failed to show any results with scientific certainty. Therefore,
> it is worthwhile to re-investigate their work, to build on what they have
> done.
>
> Romer and Beisenherz recommended 180 days (6 months), I have three months.
> I hope you are right Mike. Otherwise, I just might go with Greg's
> suggestion. Thanks Greg!!! This means that I am not screwed!!! :)
>
> Kind Regards,
> 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, Mike & Diane Wise wrote:
>
> > Jonathan,
> >
> > If you really push your fry, sexual differences can be seen within 3 months - at
> > least some of the males will start to show their secondary sexual
> > characteristics. At this age they should have visible testes or ovaries.
> >
> > Römer & Beisenherz have shown that temperature AFTER spawning is the primary sex
> > determinant in most apistos, including A. borellii.. (See my post to this list on
> > 11/29 that cites reference).
> >
> > Mike Wise
> >
> > jonathan wrote:
> >
> > > I just thought that I would keep you all updated. I'm involved in the
> > > largest non-commercial Apistogramma borellii breeding project I've ever
> > > seen. I've got five 25 gallons of these cranking out clutches of eggs at a
> > > rate of almost one a day. I've got eight 20 gallon rearing tanks set up
> > > with a clutch in each. This shall be fun. I have to get them to grow as
> > > fast as possible, water changes daily with three feedings per day. If you
> > > wonder why a hobbyist would dedicate so much time to this (almost a full
> > > time job), it's my honours BSc thesis. Anyone have any thoughts on how
> > > long it will take for these fish to reach a size that will show sexaul
> > > dimorphism? Any biologists out there have any idea whether sex can be
> > > determined upon dissection if they are not sexually mature? I am
> > > investigating environmental sex determination by pH and temperature, (and
> > > reproductive behaviour in the P generation).
> > >
> > > Kind regards,
> > > 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
> > >
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> >
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