S. Kakoolaki - Iranian Fisheries Science Research Institute (IFSRI), Agricultural Research Education and Extension Organization (AREEO), Tehran, Iran.
I. Sharifpour - Iranian Fisheries Science Research Institute (IFSRI), Agricultural Research Education and Extension Organization (AREEO), Tehran, Iran.
B. Ghaednia - Iranian Fisheries Science Research Institute (IFSRI), Agricultural Research Education and Extension Organization (AREEO), Tehran, Iran.
F. Ehteshami - Iranian Fisheries Science Research Institute (IFSRI), Agricultural Research Education and Extension Organization (AREEO), Tehran, Iran.

Nowadays, Shrimp farmers are suffering from wide spectrum of disease in type of viruses, Bacteria, and parasites. Certain parasites can enforce severe mortalities in shrimp. Among these, protozoa are also very important. The objective of our study was to determine the signs, occurrence, and intensity of unknown microorganisms. The experimental design included three groups, one treatment as infected shrimp or group B and ۲ controls with non- infected but exposure to White Spot Syndrom Virus (WSSV) shrimp as group A and non- infected non - exposure to WSSV shrimp as group C in triplicate. The results revealed that unknown-miccroorganisms associated with a decrease in hyalinocytes and large -granulocytes (less than ۸%) and a considerable increase in semi-granulocytes in group A and B in contrast to group C that Hyalinocyte increased. This infection made the shrimp susceptible to WSSV disease. It is believed that Hemocytosis causes a condition which can result in a rapid mortality among susceptible species, P. indicus when exposure to WSSV is occurred.

Shrimp, Penaeus indicus, Unknown microorganism, Intrahemocyte, Mortality