Re: [Killietalk] daphnia eggs

[Barry Cooper <bjc3 at centurytel_net>]

John,

the point is that there are no standardized ways to collect ephippia, 
which is apparent from the manual. It does give general guidance for 
stimulating their production, such as crowding the culture. The ephippia 
would be in the sediment, but isolating them seems to me to be well 
beyond the capabilities of the average hobbyist. Probably the best that 
can be done is to store the sediment. Again, the manual states that no 
standard hatching conditions have been established. In other words, the 
whole thing is a very inexact science.

I am not sure why you want to do this. My own experience is that daphnia 
cultures come back each year. When I lived in upstate NY I had a 300 gal 
water trough containing a daphnia culture. That would bloom during the 
spring-summer-fall and freeze solid in the winter. Each spring the 
daphnia returned, not doubt from ephippia in the sediment. The winter 
freeze and spring thaw were part of the conditions that allowed them to 
hatch.

If the experts who wrote that manual don't know exact procedures for 
producing and hatching ephippia, I think you can assume that the 
knowledge doesn't exist. The best you can do is follow general 
guidelines as offered in the manual and by people like Joe Bulterman.

Barry

Barry J. Cooper
Sweet Home, OR 97386



J. C. wrote:
>  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
>  
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