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Re: Live Foods Digest V2 #228
Hi George,
Your description of winter and summer ephippia intrigues me. I have done
a lot of study regarding Daphnia (I have access to one of the biggest
libraries in europe due to legal deposition), but I don't think I've come
across this phenomenon. What species of Daphnia produce these two types of
ephippia? I would be very interested in any info you could give me, as my
own practical experience is based on just two species, Daphnia pulex and
Daphnia magna.
Regards,
John
On Thu, 15 Oct 1998, George Slusarczuk wrote:
> Hello John,
>
> I agree with you, that many of the recipes for raising live foods are
> partly "voodoo", because we don't know what is it that makes them tick!
>
> In absence of contrary evidence, I would assume that the directions are
> honest, as far as *that* particular person's experience goes. Because
> few, if any, conduct multiple reproducible experiments, it's mostly a
> "one person's recipe" and many other conditions will produce same or
> better results.
>
> Many (most?) Daphnia in our latitudes (NY) produce *two* kinds of
> ephippia: summer ephippia, when the water warms up too much for their
> liking -- they hatch when conditions improve, and winter ephippia, that
> normally need several freeze-thaw cycles to hatch.
>
> So, people's experience with ephippia can be, and probably is,
> different, depending on exactly which critter, which local strain, and
> which water conditions they have.
>
> Best,
>
> George
>
>
>
> > Hi John,
> >
> > I just looked through that list of sites and though I didn't find anything
> > new, I did find some things that bothered me - I hate it when sites that
> > claim to be reliable and informative tell people how to look after
> > daphnia or about their biology and the information is crazy. Commerical
> > sites seem to be particularly guilty of this. For example Daelco claim
> > that getting ephippia is the end of the world and that they'll never hatch
> > unless frozen and thawed and/or heated up repeatedly. This really annoys
> > me because it's just plain garbage. I've found that most of the embyros in
> > ephippia will hatch within a 10 days if kept at around 72F in good daphnia
> > water. This goes for magna and pulex (my two favourites). A certain
> > proportion of the embryos take a lot longer to hatch and my guess is these
> > are the ones which are triggered by freeze/thaw. This kind of information
> > leads to people just throwing out a dead culture for no good reason.
> > There were other foolish bits of advice amongst those sites (the main one
> > that comes to mind was the no-water change advice on one of the commercial
> > sites). Another site claimed that ephippia production had nothing to do
> > with the presence of male daphnia. I often wonder how people think up this
> > stuff :).
> >
> > John
> >
>
---
"Language has not the power to speak what love indites:
The soul lies buried in the ink that writes."
eirinn at valhalla_com (http://www.maths.tcd.ie/~jpc)
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