The influence of temperature and salinity on the cyst hatchability of Phallocryptus spinosa

This study was carried out in order to determine the hatching rate fluctuations of Anostraca ( P h a ll o c r y p t u s s p i n o s a )cysts of Khasellou pools around Azarshahr under laboratory conditions.The culture medium was considered as decholorinated tap water and examined salinity and temperature treatments were 18, 23, 28 g/l, EPA solution and 15, 20, 25 ◦ C, respectively, that were near to observed ranges in natural habitat. Also, 24 hour light regime and 2000 lux were provided to obtain maximum hatching rate during the experiment. The results revealed that hatching percentage was increased by reduction of temperature and salinity on the culture medium from 25 to 15 ◦ C, and from 28 to 18 g/l, respectively. Maximum hatching rate was observed at 15◦ C and 18 g/l on the 5 th day as 5.33%. The results showed that the hatching process was occurred continuously on multiple times, so that less than 10% hatching was observed in each phase during the hatching period. Therefore decrease in water temperature and salinity could influence on hatching rate. Hatching percentage of P.spinosa cysts was more successful when sampled together with dry sediments of their habitat without separation of sensitive cysts that could be related to the creation of different grades of diapauses on their cysts. This viability can guarantee the permanent survival of these fairy shrimps in temporary stressful vernal pools.