Effects Of Acute Handing Stress On Head Kidney Immune Function In Farmed Largemouth Bronze Gudgeon(Coreius Guichenoti)

In order to probe into the effect of stress on the immune function of head kidney, an experiment of artificial simulation of handing stress on cultured largemouth bronze gudgeon (Coreius guichenoti) was conducted in the present study. The methods of light microscopy, electron microscopy and histology were applied to reveal the structure, cell morphology and cell number of head kidney of both normal and stressed largemouth bronze gudgeon. Simultaneously, the spectrophotometry was used to post out the activity of three immune enzymes (ACP-acidic phosohatase, AKP-alkaline phosphatase and CAT-catalase) in blood and head kidney of both normal and stressed Largemouth bronze gudgeon. The change of these characteristics after handing stress (0.1h,4h and24h) was mainly discussed in this study.1) The head kidney of largemouth bronze gudgeon was divided into two parts, left and right sides, which were located in the chest out of abdominal membrane and were sparated with the intra-abdominal kidney clearly. The normal head kidney here comprised lymphatic tissue, hematopoietic tissue, blood vessels, melano-macrophages and interrenal tissue except nephrons. And the tissue and cell morphology were normal and regularly distributed. By comparison, the handling stress (0.1h and4h later) resulted in signifiant increase of melano-macrophage population (P<0.01), formation of melano-macrophage centres, significant enlargement of the interregnal cellular and nuclear areas and nuclear diameter. However, at24h after the stress, the number of melano-macrophages as well as the interregnal cellular and nuclear areas and nuclear diameter decreased and they were smaller than those in the normal fish (P<0.01).2) Five types of cells including erythrocytes, lymphocytes, monocytes, neutrophilic, granulocyte and thrombocytes were identified in the normal head kidney. The stress led to alteration of the cell morphology and number in organ. Firstly, an increase of irregular erythrocytes, unclear nuclear ring, disappeared nuclear membranes, heterogeneous cytoplasm density, vacuole and a large number of lysosomes in some erythrocytes. In the cytoplasm of lymphocyte, the number of lysosomes increased, the number and volume of mitochondrias decreased, and unclear membrane, deformational cristae and augmented endoplasmic reticulum in part of mitochondrials appeared; Chromatins in nuclei of monocytes decreased, cell debris occurred, vacuole and particulate matter increased, endoplasmic reticulum scattered, and number of mitochondria in cytoplasm of monocytes reduced. There were vacuoles, increased rough endoplasmic reticulum and scattered granules in the cytoplasm of the Ⅰ-type granulocytes; and some granules were wrapped in transparent vesicles. There were without nuclei, heterogeneous cytoplasm density, vacuoles, appeared filaments near the center, a significantly increased lysosomes, smaller granulocytes in majority of Ⅱ-type granulocytes. Thrombocytes had no obvious changes. Secondly, the number of erythrocytes, neutrophilic granulocytes and basophilic granulocytes decreased continuously after the handing stress, the number of lymphocytes and monocytes increased at0.1h after the stress but decreased subsequently, the number of thrombocytes increased at all time. Overall, the present study indicates that the structure and cells in head kidney significantly changed in a short time (0.1h and4h) after handling stress, while some biological functions in24h gradually returned to normal.3) The stress led to the change of the activity of ACP, AKP and CAT in blood and head kidney of largemouth bronze gudgeon. The activity of ACP in blood decreased persistently after the handing stress and was significantly lower than that in normal individuals (P<0.05), while the activity of ACP in head kidney increased at0.1h after the stress but decreased subsequently. The activity of AKP in blood decreased at0.1h after the stress but increased at4h and24h, at the same time, the activity of AKP in head kidney increased at0.1h after the stress but decreased subsequently. The activity of CAT in blood increased at0.1h and4h after the stress but decreased at24h. The activity of CAT in head kidney was highest at0.1h after the stress, and subsequently decreased at4h and24h. The activities of ACP and CAT in blood and head kidney of largemouth bronze gudgeon are sensitive to handing stress, which hints that they could be used as biological indicators for stress.