On the "sex" stuff Peter, did your friend use MgCl and CaCl or was he using
the carbonate forms of these ions? Using carbonate would also increase the
pH. Long time ago {before Romer :-) } cichlid people used to think that pH
in apistos and many west africans was extremely important. I was one of
those, having proudly raised 150 male kribs and 2 females. Uwe says that
pH <can> be important, but only after temperature and it was a distant
second. Cichlid people tend to always push their temps, especially for
raising fry, so they are almost always at 84 F (29 C) or higher. (sounds
like rainbow people to some extent too). The same might also hold true for
any Ca/Mg experiments. In cichlids for sure, if you were going to try
another variable such as Ca/Mg I would run most of the experiments at 26 C,
where they know that you will start with a even ratio. Killifish
experiments - My first hand knowledge says you have to be extremely careful
in how you set up one of these. Dr. Jamie Thomerson who over the years has
graciously supplied the local club with Pterolebias, Astrofundulus,
Rachovia etc., always warned us to grade our fry, i.e. remove the smaller
ones from the bigger ones. The smaller ones were almost always the
females. If kept together the males would almost always eat the females
and we would end up with an all male batch and then go off blaming the
phase of the moon or the pH! BTW this also holds true for Cynolebias &
nothos too. I think Adrian also confirmed this with rainbows in his
article on boesemani a while back in one the ANGFA publications. Any
experiments done should carefully control for these sorts of problems. If
your friend has detailed notes perhaps they would be worthwhile sharing.
Again things such as tank size, temperature and pH in relation to this
Ca/Mg effect would be extremely important variables.
To maybe ponder Cary's ? - why is nature's purpose for this - Wayne did
mention that Romer took measurements in one of the brooks of the Rio Negro.
Temps varied from the top to the bottom from 30 C to 23 C with no pH
gradients. "The temperature gradient correlated with diff #s of apistos
and diff %'s of males". "Why this would be evolutionarily advantageous is
not obvious".
Gary Lange
Chairman Rainbowfish Study Group
gwlange at stlnet.com
<snip>.. has messed with Ca/Mg ratios with a variety of killies
> and some sicklids and found that the quantity of each ion was not that
> important, but the ratio between the two. If it were near 1:1 you get
> an even sex ratio, otherwise things get scewed. And yes, he could
> accurately measure Mg concentration. He also said that the sex ratio
> could be altered for up to 20-30 after hatching. No doubt these things
> vary, but will probably follow phylogenetic groupings (ie, species
> relatedness) to a degree.
> Tootles
> Peter J Unmack