The guts of shrimp from each treatment in both experiments were removed with fine forceps and placed on a microscope slides in 0.85% saline solution (sodium chloride). A coverslip was placed on guts, and the different development stages of the gregarine found were examined under a Leica DMLB 10 microscope (100 ). Gregarine stages were identified as Nematopsis sp. according to Kruse (1959) and Feigenbaum (1975).After 5 days, all surviving shrimp from the experiments were examined for wet mount analysis, and the total number of Nematopsis sp. gametocyts was counted. The mean number of Nematopsis sp. gametocyts and prevalence of infection for the total batch and for each treatment (beginning and end) were determined