Daphnia pulex through physical and chemical factors

Regarding the key role and importance of Daphnia in aquaculture, particularly for survival and adaptation of fishes in larval stages, a comprehensive study on hatching rate of Daphnia ephippial eggs was implemented to obtain an optimum technique. The effects of abiotic factors was investigated on the hatching response of Daphnia pulex diapausing eggs collected from live food ponds in Cultivation and Breeding Centre of Gorgan. After isolation, the eggs were kept in dry and wet conditions at 4°C for 2 months in darkness. Following the preincubation period, the eggs in each group were subdivided into 2 parts and treated with 1% NaOCl and distilled water. The effect of temperature levels (15 C, 20 C, 25 C) and photoperiod levels (12L: 12D, 24L: 0D) were identified on the hatching of eggs in AdaM medium during 15 days. Results indicated that the exposure of wet-kept eggs to 12-hour photoperiod and 25 C without soaking in 1% NaOCl, caused the maximum rate and speed of hatching.