Abstract
Were studied external structure of parasite Octolasmis sp and Balanus sp affecting crab blue swimmer water Gulf - Eastern Province of Saudi Arabia using the scanning electron microscope (SEM) and recorded the study was to study the regions of the peduncle and cervical in the parasite Octolasmis sp shown to covering surface of the body with hold arranged in the form of tapes and the cervicalis characterized as a pleated cover the same nipples and different from the rest of the body and that the capitulum and the cirriform appendages cover the thorns of different lengths, while the rest of the body covered by granules and the study showed also that the parasite Barnacles Sea Balanus sp there is in the form of personnel adjacent to the body host of different sizes in the areas of paper and legs chelicera in both males and females. And the body of the parasite is installed on the body of crab by the baseband (the area of strabismus Femip crab), which contains six appendices cirris, as well as the body of Balanus sp have calcareous structure. This is the first study in this area.