Effect of Temperature and Salinity on Production of Resting Egg in Korean Rotifer, Brachionus plicatilis (L and S-type)

Production of resting egg from the Korean rotifer, Brachionus plicatilis (L and S-type) was investigated at different temperatures (L-type ; 20, 24, 28℃, S-type ; 28 32, 36℃) and salinities (10, 20, 30 ppt). The rotifer was cultured in 25 ml test tube and fed on Nannochloris oculata. With regard to mixis rate, L-type rotifer showed higher rate at lower temperature, and the highest rate was observed at 20 ppt of salinity at each temperature of the experiment. However, for S-type rotifer, the optimum temperature and salinity were 28~32℃ and 20 ppt, respectively. The highest number of resting egg was 173 eggs/ml in 16 days at 24℃, 10 ppt for L-type rotifer and 410 eggs/ml in 14 days at 28℃, 10 ppt for S-type rotifer. The maximum number of resting egg produced per 10,000 rotifers was 8,122 eggs at 20℃, 20 ppt for L-type rotifer and 8,700 eggs at 28℃, 20 ppt for S-type rotifer. The maximum number of resting egg produced 10^8 cells of N. oculata was 50.7 eggs for L-type rotifer (24℃, 20 ppt) and 79.6 eggs for S-type rotifer (32℃, 10 ppt). The number of resting egg produced per day was 1~11 eggs/ml for L-type rotifers and 21~35 eggs/ml for S-type rotifer in 9 combination experiments. In this study, S-type rotifer is better than L-type rotifer in resting egg production, and the optimum temperature and salinity for resting egg production were 20℃, 20 ppt for L-type rotifer and 28℃, 20 ppt for S-type rotifer. This result shows the difference of Korean rotifer in the optimum condition for resting egg production from other rotifers reported earlier.