الفهرس 
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Abstract
The biology and parasitology of the blue crab C. sapidus inhabiting the Bardawil Lake have been studied. The size ranged between 65.3 to 163.2 mm in carapace width. Males outnumbered females by the ratio of 1:0.61. 87.3% of the population fell within 75 and 124.9 mm CW. Five female maturity stages were detected and no ovigerous females were recorded. The estimated size for 50% sexually mature females was 96 mm CW. The condition factor fluctuated through the year for both sexes and was related to season and size group. Relative growth parameters have been determined for both sexes. Results showed that this species is a carnivore feeding mainly on Mollusca, Crustacea and Pisces. The gastric mill structure was morphologically investigated and its seven articulated ossicles were examined and photographically illustrated. The study revealed that C. sapidus of Bardawil Lake suffers from the bitter crab disease as a result of infection with the parasitic dinoflagellate of the genus Hematodinium. Molecular analysis was applied to infected crabs. Infections were significantly more predominant in immature individuals and host sex did not influence the occurrence of the parasite. Intensity of infection varied among molt stages. The parasite invaded the haemocoel and the connective tissues of most organs through the haemal spaces. Hisopathological investigations of hemolymph, heart, muscle, hepatopancreas and gill were carried out. Cells of the parasite underwent characteristic progressive changes consistent with the recognizable stages of Hematodinium sp.: sporoblasts, arachnoid sporonts, vermiform plasmodia, ameboid trophonts and filamentous trophonts. Despite the prevalence of bitter crab disease, the study concluded that environmental conditions in Bardawil Lake fulfill the requirements for the flourishing of C. sapidus.