Cytology And Histochemistry Of Lymphoid Organ And Haematopoietic Tissue, And Effect Of Foreign Materials On Their Function In Fenneropenaeus Chinensis

The lymphoid organ of penaeid shrimp is the important organ related with the shrimp immunity. It can eliminate the pathogenic organisms invading the host efficiently. Therefore, the investigation on lymphoid organ is the main portion of study on shrimp immune mechanism. The development of lymphoid organ was studied by histological technique in Chinese shrimp Fenneropenaeus chinensis firstly, and cytological and histochemical methods were used to investigate the lymphoid organ of adult shrimp.The results showed that the lymplioid organ was composed of lymphoid tubules derived from the end of subgastric artery. At the third stage of mysis, the subgastric artery originated from the extension of anterolateral artery endothelia at the position ahead of heart, and the dorsal mesodermal cells of larvae accumulated around endothelia as the stromal matrix cells. When larvae grew to 1.8cm, the ramification without tubule lumen appeared at the end of subgastric artery extending to hepatopancreas foreside. The lymphoid organ of 3.5cm juvenile shrimp consisted of at least ten lymphoid tubules, and its morphology was similar with that of the adult.The stromal matrix cells of lymphoid tubules had developed heterochromatin, extranuclear granules, and abundant organelle.. They also had positive PAS reaction and a-naphthyl-acetate esterase activity, but had no phenoloxidase (PO) activity. In the haemal sinuses of larger lymphoid organ (Long Diameter > 2mm), there were many cell clumps, spheroids. The spheroid cells had developed heterochromatin, but no extranuclear granule, and had weak PO activity. Some interim forms of necrotic spheroid cells also were observed. It was presumed that the stromal matrix cells oflymphoid tubules separated from tubule walls, accumulated in hemal sinus, and formed spheroids to clean the foreign materials further, which was physiological reaction of shrimp to environmental pressure. After the spheroids appeared, some stromal matrix cells showed poorly or unstained cytoplasm around the nucleus, and many necrotic cells also were observed in tubules under TEM. Some tubules presented weak PO activity, and this might resulted from the settlement of small granular haemocytes in tubules, which became the supplement of stromal matrix cells.The haemocytes are not only the undertaker of cellular immunity, but also the provider of humoral immunity. The study on ontogenesis and differentiation of haemocytes administers to the discussion of their classification and function. The histological method was used to locate the distribution of haematopoietic tissue (HPT) in larvae, and that of the adult was investigated by cytological and histochemical methods in F. chinensis. The results showed that HPT mainly located on dorsal and dorsolateral sides of the stomach surrounded and in ventral region at the base of the appendages. The HTP cells were classified into three types under TEM, the stem cells with high cytoplasm to nuclear volumetric ratio and developed euchromatin, young small granular haemocytes containing striated granules and homogenous granules, and young large granular haemocytes only containing homogenous granules. A series of intermediate cells from stem cells to two young haemocytes respectively were observed, so it was presumed that small and large granular haemocytes were differentiated from stem cells respectively in F. chinensis. There was obvious difference between young haemocytes released from HPT and circulatory haemocytes, and the young haemocytes would develop and mature further in the circulatory system. The hyaline haemocyte might represent the immature stage of small granular haemocytes.The immune revulsants are often used in the study on humoral immunity factors of shrimp. The white spot syndrome virus (WSSV) and zymosan A were used as revulsants to stimulate the Chinese shrimp F. chinensis in this study, and several enzyme activities in lymphoid organ, hepatopancreas and gill, total haemocyte count, and mitotic index of HPT cells were measured to indicate their function in hostde...