Re: Sex Ratios (and E-mail Test)

[Rich Grenfell <rgrenfell@sbcglobal.net>]

I have also been reading Uwe's book for this very
reason. I have been working with Diplotaenia, and the
sex ratios have been something that interested me. I
was told that the cooler the water the more females. I
like trios so I tried for females. The temp was kept
at 76 degrees. Of 60 fish I got 13 females. I think
there could have been more, but a dozen or so did not
grow out, and ended up being runts. I also noticed
that they did not grow very quickly, and instead had
growth "spurts". I suppose this could perhaps be the
lower temp? The growth may also have been altered
because I hatched in rain water and grew them in tap. 
I have since purchased an RO unit that arrived today
(THANKS MAX!) so i will be able to produce the
suggested water chemistry as well.I planned to sell
everything but decided to keep 3 pairs to try again
under the conditions suggested in Uwe's book. My
breeders have since died, so I will be using 3 pairs
of F2 siblings.

Rich

P.S. I have some males available (cheap) in case you
were interested!! LOL!!!


--- Mike & Diane Wise <apistowise@fgn.net> wrote:
> David,
> 
> I don't know if you can equate plants & animals.
> Animals are much more mobile &
> will not need the delay of 1 sex over the other to
> disseminate their genetic
> material. Römer has not only studied the physical
> effect, but also the
> ecological effect of temperatures on sex
> determination in apistos - both in the
> laboratory & the wild. He found that 26ºC/79ºF was
> the optimum temperature for
> most apistos. Higher & lower temperatures retarded
> growth & maturity. He also
> found that primary predators on apistos tended to
> prefer higher & lower
> temperatures, so for some reason 26ºC has few
> predators. Römer has a good review
> of his study in his book "Cichlid Atlas" (sections
> 4.2.2.1 through 6). It can
> explain his ideas better than I.
> 
> Mike Wise
> 
> "David A. Youngker" wrote:
> 
> > Hey All -
> >
> > Well, I've suffered my last problem with
> MindSpring, and I hate having to
> > leave an address that's been maintained for so
> many years, but I'm moving to
> > BellSouth as an ISP. Changing addys means testing
> some of my subscriptions
> > for continuity, but in this case it also allows
> the opportunity to ask a
> > general question concerning Apisto biology and
> biotopes.
> >
> > Many of the Apistos we keep seem to have a skewed
> sex ratio within brood
> > batches that varies with temperature. Mayland and
> Bork reported on Uwe
> > Romer's studies, and we've bandied them about at
> times, and the pattern
> > seems to follow that the cooler the water the
> greater the percentage of
> > females. I've also noted it within my own breeding
> efforts, and it's an
> > easily observed phenomenon in my tanks as I tend
> to keep them on the cooler
> > side to extend the Apistos' longevity somewhat.
> And I've been pondering the
> > situation a little but can't come to any definite
> conclusions because I'm
> > lacking some fairly basic information that would
> help lead to an end point.
> >
> > The evolutionary reason behind the ratios could
> depend on one of two logical
> > factors. It could be an effort to ensure the
> availability of ripe females
> > for the shorter-lived males (whose colors, etc.
> tend to cause them to become
> > snacks more often than females) or it could be a
> way to extend the genetic
> > pool by allowing females more time to expand their
> territories before
> > encountering a male.
> >
> > I know that some plants with the capability of
> self-fertilization often have
> > their male and female structures mature at
> different times to prevent
> > inbreeding as a rule of habit. This usually means
> the males first so that
> > the pollen can travel some distance from the
> originating stand and ensure
> > genetic diversity. Something along these lines
> could be at work within the
> > genus Apistogramma, leading to the thought of
> extended territories. In our
> > own efforts, when a breeding doesn't "work" we
> often assume the male isn't
> > "ready", but perhaps instead the _females_ (which
> most often come from the
> > same broods and have the same time for development
> with us) are the true
> > culprits.
> >
> > Is there a source of field collection data that
> samples the environments at
> > times _other_ than prime collection periods? I
> know that Apistos, like other
> > Amazonian fish, are far easier to collect during
> the dry season when water
> > levels are down and populations are concentrated,
> and conversely the wet
> > season makes collection nearly impossible in a lot
> of areas. But perhaps
> > some of the collectors are out there getting
> "early starts" on the season
> > and have some of this data within their field
> notes.
> >
> > It would be an interesting exercise (at least to
> me) to try to see how much
> > time the females would normally have to populate
> and spread through an area
> > before the warming waters start to increase the
> population of the males...
> >
> > David A. Youngker
> > youngker@bellsouth.net
> >
> >
>
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