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daphnia myths
>From: John Clare <clarej at tcd_ie>
>Subject: Re: Daphnia web sites & their myths
>
>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 :).
>
As I've suggested in several messages to this and other lists and to
individuals, no two situations are the same. I use a bubble wand in my
tanks; one of the referenced sites suggests air bubbles kill. I think the
current (and lots of light) are very helpful. I've also recommended water
changes. I've sugested people split their starter culures up and try
different things. I think there's so much difference in water, etc and
maybe in "strains" of daphnia that you really have to experiement to find
what's right in your own situation. I know I killed off several starter
cultures before I found what works for me. And I've yet to get enough
dapnia pulex to have a good source of food for fish... I get just enough to
keep the culture going. Very irritating. And I killed off my suposedly
unkillable monia culture.
Now dahnia magna, on the other hand, is realy appreciated by my rainbow
darters. It's worth the effort to raise them (the daphnia and the darters).
It comes down to this: If you want the truth, you have to fish through a
lot of information (yes, that's a pun). I've never tried to hatch
ephippia. I just believed the freeze/thaw stuff and moved on. Now, should
the occassion arise, I know to try.