الفهرس 
Daphnia (The key species in the aquatic food web)Only 14 pages are availabe for public view
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Abstract
The water fleas Daphnia (Crustacea, Cladocera) are small (< 6 mm) planktonic crustaceans that often dominate zooplankton biomass in freshwaters all over the world. Daphnia are keystone species since they are very efficient grazers on phytoplankton, bacteria and protozoa.It is a major food source for many planktivorous fish species and therefore represents a key species in the aquatic food web.First section:1- Occurrence, abundance and species composition of Daphnia species:The surveillance study proved that the collected Daphnia involved three species, all belonged to Suborder cladocera,Infra order Anomopoda Latreille, 1829, family: Daphniidae Straus, 1820. The three species were identified as Daphnia long ispina Muller, 1785; Daphnia magna Straus, 1and Daphnia pulex Brooks, 1957.The results also showed that the three species were recorded from 4 sites. D. longispina and D. magna were the most prevalent species; they were recorded from 3 sites (Kafr Elsheikh, Basion and Al Sharqiyah, in the case of D. longispina and Kafr El-sheikh, Damietta, Al Sharqiyah in the case of D.magna).