Date: 15 August 1998
To: BRINE-L@UGA.CC.UGA.EDU
QUESTION:
If you buy Artemia cysts in bulk, can you freeze the ones you don't use for future use? Will this harm them?
Russell Hammond <harvester1@webtv.net>
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COMMENTS 1:
My local advisor, David Kawahigashi, is biologist at SF Bay Brand. He advises never freezing eggs, but refrigerate them for extended storage. He says freezing will harm them.
I have also found that one needs to take them out and allow to come to
room temp, before opening the can or bag, or the dew can damage the cold eggs.
Wright Huntley, Fremont CA, USA, 510 494-8679
huntley1@home.com
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COMMENTS 2:
It seems that advice on cold storage of Artemia cysts depends on their
origin:
Sanders (Utah) recommends storage at -20 C for longer than a
month, at 0 C for up to a month and 4 C up to a week.
The cysts should be thawed from -20 C for 24 hours before hatching.
George Slusarczuk <yurko@warwick.net>
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COMMENTS 3:
Freezing of Artemia cysts for long term storage is perfectly good. It will not harm the cysts. Some strains on the market will require a few days up to a week at ambient temperature before incubation. You should test your strain to be sure if this is required. If the cysts will be used within 6 months a household refrigerator will suffice. It is for sure that our studies indicate that cold is the greatest protector and preserver of the quality of Artemia cysts.
(...)
David Kawahigashi is correct in that you should protect the cysts from
moisture that you intend to store or bring out of cold storage but we have kept cysts at -18 degree C for years without loss of hatchability. I think if you readdress the issue with David K. he is saying that it is not necessary to keep them frozen but it is necessary to keep them cold. Some cyst material will deteriorate very quickly at ambient and therefore must be stored either refrigerated or frozen. I believe that the misunderstanding occurs when someone removes cysts from a freezer and tries to incubate them right away....some material is still in diapause and will not wake up quickly.
(...)
We have been doing long term cyst storage analysis since 1992 on a variety of strains: Great Salt Lake, CIS, Siberian, Canadian, San Francisco, Mexican, Brazilian, Argentinan, Vietnamese. Most of these cysts are stored at -18 degree C, 0-4 degree C, 22-24 degree C and hatchery temperature at 30 degree C. Most quality processed cysts will do fairly well at all temperatures for a couple (2) months and then a slow deterioration in hatching quality will begin. Depending on the cysts source determines the slope of the decline.
You are correct in the commercial storage economics of storing at freezer temperatures (-10-20 C) or at 0-4 C.....It would cost us about $3-4, 000 extra each month during summer to run our freezers at that temperature....all for no advantage.
What would happen with the Great Salt Lake cysts is that the ones collected in September and October (sometime up to mid November) had not broken dormancy on the lake and would store VERY well. After the cysts would break dormancy on the lake (after the cold weather really sets in) these cysts when processed would show very unstable storage at ambient or warmer temperatures. The late
harvested cysts always needed to be cold stored.
With the risk of being redundant....know the characteristics of your cysts by either inquiring of your wholesaler or the processor.
(...)
I think that if you just divide the open tin of cysts into small freezer ziplock bags you will have no problem. Certainly the warming and freezing is not the best on the diapausing or quiescent cysts.
Howard W. Newman
<BShrimp@aol.com>
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COMMENTS 4:
I would concur with Howard, though I haven't seen any scientific evidence to support an "optimum" temperature. Our company, as well as several other brine shrimp companies that I am aware of, maintain both unprocessed and processed cysts at commercial storage facilities that are maintained at a constant 3-5 C) for over two years (a long time in our business) without appreciable loss of "hatchability." I'm not opposed to freezing, it's simply a question of economics and space. I think that the key word here is
"constant."
Tim Troy <ETROPLUS@aol.com>
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COMMENTS 5:
The implication here, is that my (possible) slow hatch-rate degradation could be because I freeze or refrigerate a whole can, but warm it periodically to extract a couple of weeks worth of eggs. That's hardly "constant."
If that is true, it sounds like dividing the bulk eggs into multiple
hermetic packets and then freezing them would be best. Then each
packet is only brought to room temperature once.
Wright Huntley, Fremont CA, USA, 510 494-8679
huntley1@home.com
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COMMENTS 6:
I guess I was only partially correct in interpeting the correct temperature for cyst storage (as we have learned from Tim and Howard). The industry standard is to store cysts at refrigeration temperatures (although maybe Sanders uses sub-zero temperatures). My understanding is that since the unprocessed Utah cysts have already "over-wintered" at sub-freezing temperatures and broken diapause, it was not necessary to refreeze them again and best to keep the cysts at "cool" temperatures to reduce moisture in the product. If the difference between cold storage temperatures is purely economics, then I guess that both refrigeration and sub-freezing
temperatures are acceptable for storing cysts and I stand corrected that
storage at sub-freezing temperatures may actually harm hatching quality.
David Kawahigashi
tech@BRINESHRIMPDIRECT.COM