Tech Talk 100
or brine shrimp is commonly used as a larval feed for several aquatic species. In order to ensure the highest nutritional value, Artemia
cysts should be decapsulated prior to hatching. This will disinfect the cysts, remove the chorion (the indigestible portion of the cyst) and will also reduce the amount of energy that the Artemia
has to exert to hatch. The process increases the nutritional value and hatch rate of the newly hatched Artemia
and minimizes the risk of bacterial infections and gut obstructions by the chorion.
There are two common methods used to decapsulate the cysts. For both of the methods described, the first step is to hydrate the cysts by soaking them in either fresh or salt water for one hour. Dry cysts have a "dimple" that makes uniform removal of the shell difficult.
This method uses household bleach (6% sodium hypochlorite solution) or industrial chlorine (11% sodium hypochlorite solution). 15 g of hydrated cysts are placed in a container with 300 mL of 6% hypochlorite solution. The cysts are then placed on a magnetic stirrer in a container of the bleach for approximately 3–5 minutes or until the cysts turn an orange/brown color. Immediately drain cysts into a 120-micron sieve and wash with fresh or seawater until no smell of chlorine remains (about 5 minutes). Hatch as usual.
Chlorine/Sodium Hydroxide Method:
This method uses full strength seawater, sodium hydroxide (NaOH, 50% solution), and industrial chlorine (11% sodium hypochlorite solution). Since the chemical reaction that takes place is exothermic (it generates heat) the seawater and chemicals used should be very cold (40–45°F/4–7°C ) to prevent heat damage to the cysts. For each 100 grams of cysts to be decapsulated, place 15 mL of 50% NaOH, 550 mL of 11% chlorine and 800 mL of chilled seawater in a container with heavy aeration or a magnetic stirrer. Keep in mind that there can be a lot of foam and the container should be large enough to prevent overspill. Add the hydrated cysts and watch for the cysts to turn an orange/brown color (3–5 minutes). Immediately drain cysts into a 120-micron sieve and wash with fresh or seawater until no smell of chlorine remains (about 5 minutes). Hatch as usual.
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