Re: [Killietalk] daphnia eggs

["J. C." <hillbillynursery at yahoo_com>]

 Barry, I have read it and even said so in my first
response to the email list. Here is the intire section
you mentioned and no where does it give lengths or
procedures how to get them to produce resting eggs.

 quote:Resting eggs are interesting material for
storage, shipment and starting of new Daphnia
cultures. The production of resting eggs can be
initiated by exposing a part of the Daphnia culture to
a combination of stressful conditions, such as low
food availability, crowding of the animals, lower
temperatures and short photoperiods. These conditions
are generally obtained with aging populations at the
end of the season. Collection of the ephippia from the
wild can be carried out by taking sediment samples,
rinsing them through a 200 µm sieve and isolating the
ephippia under a binocular microscope. Normally, these
embryos remain in dormancy and require a diapause
inhibition to terminate this status, so that they can
hatch when conditions are optimal. Possible diapause
termination techniques are exposing the ephippia to
low temperatures, darkness, oxygen and high carbon
dioxide concentrations for a minimal period of several
weeks (Davison, 1969).

There is still no standard hatching procedure for
Daphnia. Generally the hatching process is stimulated
by exposing the ephippia to higher temperatures
(17-24°C), bright white light (70 W.m-2), longer
photoperiods and high levels of dissolved oxygen. It
is important, however, that these shocks are given
while the resting eggs are still in the ephippium.
After the shock the eggs may be removed from the
ephippium. The hatching will then take place after
1-14 days.
 end quote.

  I have even done web searches which turn up
thousands of hits to only find daphnia being used for
pollution test and such. I did the homework and got
nothing so was hoping for answers here.

                    Later, John



--- Barry Cooper <bjc3 at centurytel_net> wrote:

> John,
> 
> I have twice before suggested that you refer to the
> FAO Live Foods 
> Culture Manual, to which there is a link in the
> Library section of the 
> AKA web site. See the section entitled "6.1.5.
> Production and use of 
> resting eggs".
> 
> BC
> 
> Barry J. Cooper
> Sweet Home, OR 97386


John Cox of Cumberland Killifish
 Honey Robber beekeeping and removal services
 
 Please join A Fishy World my new email group all
 about fish at AFishyWorld-subscribe at yahoogroups_com

__________________________________________________
Do You Yahoo!?
Tired of spam?  Yahoo! Mail has the best spam protection around 
http://mail.yahoo.com 
Join the AKA at http://www.aka.org/aka/modules/content/index.php?id=9.
Archives are at http://fins.actwin.com/killietalk/
Modify your subscription at http://www.actwin.com/mailman/listinfo.cgi/killietalk