ROTIFER RESTING EGGS
The development of aquaculture of commercial fish and shrimps continues to enhance both productions and growth of larvae. The important factors in supporting the success of operation are the supply of excellent food and availability of food in numbers, good quality and suitable size for the mouth of larvae. Rotifer, as zooplankton, is an excellent natural food for larvae of fish and shrimp. It has a unique reproduction, both sexual and asexual. The aquaculturists could exploit the capability of rotifer to produce two kinds of food. Rotifer’s asexual reproduction can produce rotifer that is directly given to the larvae, however, rotifer’s sexual reproduction delivers formation of resting egg that could be preserved and hatched, at a desired time. On the other hand, loss of hatch-ability is frequently occurring that causes low ability of the natural food. Besides the right handling in producing resting egg, it should be carefully observed that the low hatching rate is resulted by contamination of some bacteria or other microbial.
This research are aimed :
- to examine the effectiveness of disinfectant in decreasing the loss of hatch-ability,
- to determine the optimum concentration and the most effective kind of disinfectant.
The S-type of rotifer Brachionus rotindiformis was used and taken from Meras Ponds, district of Bunaken, using plankton-net, which then isolated and cultured in laboratory. In addition, a preserved resting egg in can (from Nagasaki, Jepang strain) was used in this experiment. Culture of rotifer was carried out with batch culture and semi-continuous method in 20 ppt salinity of seawater under laboratory condition (250C, light intensity using 80 watt TL lamps and photoperiod 24 L : 0 D). This rotifer was fed daily with microalga Tetraselmis sp. After 12 days, the culture was checked for formation of resting eggs in bottom of bottle, pipetted out under microscope. Daily collected resting eggs were put into black film bottle 5 ml seawater 20 ppt and kept in refrigerator 50C.
Treatment for resting eggs with disinfectants to enhance its hatch-ability was applied to freshly resting eggs of Meras strain, freshly resting eggs of Nagasaki strain and preserved Nagasaki strain resting eggs in can. The resting eggs were put into petridish containing 5 ml seawater with 15 ppt salinity, about 30 individuals for each petridish and for each treatment. Several disinfectants were used namely, Sodium Hypochlorite (NaOCl) 1 ppm, NaOCl 2 ppm, Kalium Permanganate (KMnO4) 0,01 g/l, KMnO4 0,03 g/l, Caporiet 0,05 g/l and 0,10 g/l, besides the 30 resting eggs in petridish were not treated with any disinfectants as control.
Culture of rotifer was carried out through 2 systems, batch culture and semi-continuous method.
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