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Effect of Decapsulation on Viability and Hatching Performance of Artemia Cysts at Different Salinity Levels

S.U. Ahmed
Brackishwater Station, BFRI, Khulna-9280, Bangladesh

M. Kamal
Department of Fisheries Technology, BAU, Mymensingh

M.N. Islam
Department of Fisheries Technology, BAU, Mymensingh

M.A. Rahman
Department of Fisheries Technology, BAU, Mymensingh

Abstract/ Executive Summary:

Artemia cysts were produced from the traditional solar salt works of Bangladesh through different fertilization treatments were tested for viability and hatching performance in different forms, such as processed and preserved, processed and decapsulated and unprocessed and undecapsulated. Decapsulated cysts performed maximum hatching (86.0%) in 20 ppt salinity during 48 hours of incubation. The hatching percentage by the unprocessed and undecapsulated cysts were very low (12.0- 18.7%) in all the tested salinity grades.

Keywords: Artemia, Decapsulation, Hatching, Salinity

Location: Great Salt Lake (GSL), Utah,USA

Start Date: 00-00-1993

End Date: 00-00-1993

Program Area: Animal Health and Management

Non-commodity: Performance

Objectives:

To find out the effect of decapsulation of different forms of locally produced Artemia cysts on viability and hatching performance.

Methodology:

Artemia cysts were produced using the strain of Great Salt Lake (GSL), Utah, USA, in the Artemia production ponds (APP) of the modified solar salt works of Bangladesh by various feeding I manuring treatments. Treatments were T₁ (Urea and TSP at a rate of 25 and 20 kg/ha/week respectively), T₂ (dried powdered and sieved chicken manure at a rate of 125 kg/ha 3 - 4 days interval in the first year), T₃ (same as T₂ applied in the second year) and T₄ (double the rate of application of T₃ of second year). Initial fertilization was done before five days of Artemia nauplii release and the quantities were different than the regular ones, such as for T₁, Urea+ TSP =50+ 20 kg/ha, for T₂ and T₃, chicken manure 500 kg/ha and for T₄, chicken manure 1000 kg/ha. Hatching of both decapsulated and undecapsulated cysts were tested in different hatching conditions : Hatching of the cysts in different salinity media : 10, 20, 30 and 40 ppt. Observation of the hatching performances of the decapsulated cysts at different time intervals, such as 24, 36 and 48 hours. Hatching of the cysts in different comparable forms like processed and preserved (not decapsulated), processed and decapsulated and unprocessed and undecapsulated (preserved). The cysts hydrated up to 2 hours in fresh water at ambient temperature ranging between 25 - 28° C (hydration time increased with decreasing temperature and increasing salinity). For hydration, 1 g dried cysts were provided per 20ml of water and aeration was made at a rate of 0.51/min. Prolonged hydration prior to hypochloride treatment was avoided because it could drastically affect the hatching rate and efficiency of the decapsulated cysts. Commercial grade sodium hypochloride (NaOCI) was diluted to 50% with sea water and 40% sodium hydroxide and was used for decapsulation. NaOH was added to increase pH above 1 0.0. Hydrated cysts were transferred to the decapsulation reagent (15 ml for 1 g cyst) and stirred well continously with a glass rod for about 10 minutes. Temperature was maintained below 40°C by keeping the decapsulation container in cold water bath. Cysts were decapsulated within 15 minutes which were immediately filtered out on a 120 ~m mesh cloth. After complete dissolution of the chorions, the decapsulated cysts were filtered off and excessively washed on a 120 micro m screen with tap water until no more chlorine smell was noticed. Hypochloride residues adsorbed into the decapsulated cysts were deactivated by dipping the cysts in 0.1 N HCl for several times. This deactivation lasts less than one minute and then cysts were again washed with tap water. Hypochloride residues were detected by putting some decapsulated cysts in a small amount of diluted starch-iodine reagent (i.e. starch, potassium iodide, sulphuric acid and water). After the completion of the deactivation and washing procedures, cysts were drained on a 120 micro m sieve and transferred into a saturated brine solution at a rate of 1 g (decapsulated cysts)/10 mi. Since upon incubated in brine, dehydrated cysts were releasing water so that brine had to be renewed after each hour of incubation. Settled cysts in the bottom were filtered through 120 micro m screen. Cysts were then poured in fresh brine solution and kept in refrigeration for future use.

Source of Information: Bangladesh J. Fish. Res., 1 (2) : 67-74, 1997

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

Decapsulated cysts performed maximum hatching (86.0%) in 20 ppt salinity during 48 hours of incubation. The hatching percentage by the unprocessed and undecapsulated cysts were very low (12.0- 18.7%) in all the tested salinity grades.

Knowledge Management: Journal