Re: [Killietalk] RE: Challange??

[Barry Cooper <bjc3 at centurytel_net>]

Koran, David HQ02 wrote:

> For starters, you probably need to culture "daphnia" in hard water or
> have calcium present in order for the animals to develop their exo-skeleton.
>  
Ahh, another oft repeated false assumption. Daphnia presumably do 
require some calcium in their environment, but the shell, or carapace, 
is NOT calcified. I quote from 
http://www.cladocera.fsnet.co.uk/morphology.htm:

"The Cladocera are relatively primitive crustaceans with their bodies 
completely enclosed by an uncalcified shell (or carapace 
<http://www.cladocera.fsnet.co.uk/female1.htm>) and having 9 or 10 pairs 
of appendages <http://www.cladocera.fsnet.co.uk/daphnia.htm> - 
antennules, antennae, maxillae and mandibles attached to the head, and 
five or six trunk limbs <http://www.cladocera.fsnet.co.uk/semmorph.htm>, 
which are using for feeding and respiration".

Personally I have had Moina cultures going for some years now in dead 
soft water. As the tubs are in the open they are filled mostly with rain 
water (I'm in Oregon, after all).

People often assume that because biological structures are hard, they 
are calcified. That is often not the case. Our finger nails, the hooves 
of horses, cattle, etc., the shell of tortoises and turtles, are not 
calcified but are composed of compacted keratin (mostly), a protein.

I'm not discouraging people from having some calcium in their culture 
water, but it is not to allow the Daphnia to form the carapace.

Barry

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