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Re: Live Foods Digest V2 #228

Hi George,

I am familiar with Pennak's book (thanks to that library), and I'm well
aware of the pulsing phenomenon in Late Spring and in Autumn. I will have
a look for any papers on ephippia to try and clarify it for myself, but I
get the distinct impression that by and large for most species there is
only one kind of ephippium and this is produced when a female is
fertilized by a male, no matter what time of the year as it is simply
dependent on the presence of males, which in turn is dependent on
environmental conditions.


On Sat, 17 Oct 1998, George Slusarczuk wrote:

> Hello John,
> It is fortunate, that you have access to a good academic library -- I
> miss that sorely! 
> Right now I can't lay my hands on the "two kinds of ephippia" paper(s). 
> But in a good library you will have access to Biological Abstracts,
> perhaps even have them online, so searching for "ephippium" and/or
> "daphnia" will get you these papers. 
> There was a spate of publications about 10-15? years ago. One
> interesting paper was from Leningrad, Russia. The authors did
> experiments on the freeze/thaw cycles, using a local strain of a
> cladoceran, can't remember which. Several Finnish workers also did work
> in that area. 
> Closer to home, R.W. Pennak in his "F-W Invertebrates of the US" refers,
> in several places, to spring and fall maxima in cladoceran populations
> and that males tend to appear in late spring and fall. Males = ephippia.
> If you find out more detail on this subject, please share. For the last
> 5 years or so, I did not try to keep abreast in that field.
> Best,
> George