| Popis: |
This project was carried out in order to determine the hatching conditions and laboratory culture methods of Fairy Shrimps (Phallocryptus spinosa). Physico- chemical factors and phytoplankton of natural habitat of this organism was investigated in Khasellou region around Azarshahr – East Azarbaijan province. The results showed that occurance and growth of fairy shrimps in their habitates were beginning from early Aprill and their survival was decreased with increasing temperature, precipitation and increasing the salinity of their culture medium. Then they disappeared. Their habitat phytoplankton contained 3 phylla and 10 genera, from which green algae enjoyed the greatest density in May. The pool salinity was around 20-17 g/l, when metanauplii was observed in early spring. In the pool containing and without fairy shrimps the oxygen concentration was high (9 mg/l) and low (2.9 mg/l), respectively. In 9 prawn ornamental fish genera, feeding with fairy shrimp showed a significant higher fecundity and hatching percentage compared to manual diets (cow liver, spinach). In all groups fed with fairy shrimp the duration of spawning time were reduced from 15 to 8-10 days and the color was enhanced. The means of cyst number per captured female also, cyst, decapsulated cyst and Naupilli diameters were mesured 142.9±19.0 cysts, 273.2±4.9µ, 242.4±3.8µ and 542.6±27.0 µ, respectively. The hatching rate was increased by reducing temperature and salinity of their culture mediums from 25 to 15 ◦C , and 28 to 18 g/l, respectively. The highest hatching was observed on 5th day at 15 ◦C and 18 g/l (5, 33 %). In addition, low but multiple hatching was observed. Therefore, water temperature and salinity affected hatching rate in this species. The hatching success of Phallocryptus spinosa cysts was better when collecting cysts together with dry sediments of their habitat without separation sensitive cysts. In addition to cold keeping and freezing, the hydration – dehydration method caused more diapause deactivation for hatching induction. The laboratory results revealed that the survival of fairy shrimps were highest at 15 ◦C (42%) and lowest at 25◦C (26%), respectively. Also, their life was inhibited in 30◦C. In different salinities, the mean survival rate were 26% (Salinity= 15 g/l) and 20% (Salinity= 25 g/l), respectively. The mean survival percentage of Phallocryptus spinosa cultured in natural habitat water (64.3%) was higher than aerated tap water (23, 3 %). Also, feeding with Nanochlorepsis caused higher survival rates. On the other hand, Beakers yeast caused higher mortality rates. Therefore, regarding to relatively high sensitivity of these species to physico– chemical and nutritional conditions of their culture medium, it is better to culture these species with expansion of their natural habitat in order to preserve their biodiversity, culture and increase stocking density with regard to environmental considerations . |
