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What is decapsulation?
The hard shell that encysts the dormant Artemia embryo can be completely removed by short term exposure to a strong hypochlorite solution. This procedure is called decapsulation. Decapsulated cysts offer a number of advantages compared to the non-decapsulated cysts.
What are the advantages for using decapsulated Artemia cysts?
For one, cyst shells are not introduced into the culture tanks. When hatching normal cysts, the complete separation of Artemia nauplii from their shells is not always possible. Unhatched cysts and empty shells can cause mortalities in fish fry as pieces of the shell or corion can be lodged in the digestive tract of the fish or shrimp.
Improved hatching percentages, by as much as 10%, can also be expected from using decapsulated cysts. This is due to less energy required for the embryo to " burst" through thin hatching membrane surrounding the embryo.
The decapsulated eggs are also thoroughly disinfected, thereby reducing the bacterial load of the hatching medium during incubation.
Lastly, the unhatched cysts (following incubation) are still edible and easily digestable by your fish. In fact, the energy content found in unhatched Artemia cysts is higher than that of a hatched, live baby Artemia. This is a very valuable course of action when Artemia cyst hatching quality is poor.
DECAPSULATION PROCEDURE
Ingredients:
500 grams Artemia cysts (do not use Russian origin cysts)
4.77 liters sodium hypochlorite (household bleach)
75 grams sodium hydroxide
2.2 liters of water
1) Hydration
Dry cysts resemble deflated basketballs under the microscope. The cysts must be fully hydrated or spherical before decapsulation is to begin. Simply hydrate the cysts in a half-bucket of fresh water with aeration for one hour.
2) Decapsulation
Dissolve sodium hydroxide in 2.2 liters of water and allow to cool. Do not add hypochlorite until ready to decapsulate. Collect the hydrated cysts in a 125 mesh sieve and drain. Add the sodium hypochlorite solution to the sodium hydroxide and water followed by the hydrated cysts.
The cyst color should change from brown - gray - white - orange within a few minutes, depending upon the strength of the chemicals and the thickness of the shell or corion. When the cysts are 90% orange, stop the reaction immediately by pouring the decapsulated cyst solution in a fine mesh bag and rinse well with lots of freshwater.
To assure that the decapsulation reaction is stopped, have a solution of .1 normal hydrochloric acid (HCl) ready to stir the cyst in for one minute. Prepare this solution by adding 65 ml of hydrochloric acid (35% active) into 6.5 liters of water. A weak solution of sodium thiosulfate can also be used to neutralize the chlorine.
Can I store decapulated cysts for later use?
Decapsulated cysts that are not used for hatching right away can be stored for later hatchings. Drain or remove all excess water from the decapsulated cysts. Add brine water (300+ ppt salinity) until the cysts are completely covered. The brine water will pull the water out of the cysts or dehydrate them again. If the cysts are to be stored for several weeks to a month, replace the old brine water with new brine water after 24 hours. Store the decapsulated cysts (in brine water) in the refrigerator for up to one month.
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