What are decapsulated brine shrimp eggs?
The hard shell, or chorion, that encysts the dormant brine shrimp 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 non-decapsulated cysts.
Advantages of Using Decapsulated Brine Shrimp Cysts
For one, cyst shells are not introduced into the culture tanks. When hatching normal cysts, the complete separation of brine shrimp 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 chorion can be lodged in the digestive tract of the fish.
In some cases, improved hatching percentages (by as much as 10%) can also be achieved from using decapsulated cysts. This is because less energy is required for the embryo to "burst" through the 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 digestible by your fish. In fact, the energy content found in unhatched brine shrimp cysts is higher than that of a hatched, live baby brine shrimp. This is a very valuable course of action when brine shrimp cyst hatching quality is poor.
Decapsulation Procedure
Ingredients
- 454 grams (1 pound) brine shrimp cysts
- 4.33 liters sodium hypochlorite (household bleach)
- 68.1 grams sodium hydroxide
- 2 liters of water
Process
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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 to two hours. -
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.
This step, in which the chorion is dissolved or oxidized, is exothermic (generates heat); and in order to prevent the solution from exceeding a temperature that will be lethal to the embryos, ice should be added (cubed or otherwise) to maintain a reaction temperature below 100°F.
The cyst color should change from brown to gray to white to orange within a few minutes, depending upon the strength of the chemicals and the thickness of the shell or chorion. 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 fresh water.
To assure that the decapsulation reaction is stopped, have a solution of .1 normal hydrochloric acid (HCl) ready to stir into the cyst 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.
Storage of Decapsulated Cysts
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.