本研究以吳郭魚 (Oreochromis mossambicus) 為實驗樣本，探討重金屬鎘對魚類血球某些形質之影響。包括紅血球溶血現象 (haemolysis)；紅血球細胞膜強度與淋巴球數量等。吳郭魚紅血球在低張溶液 (0.24 %之生理食鹽水) 發生完全溶血現象，而在0.32 %之生理食鹽水則不會破裂。由於溶血程度與細胞膜之強度有關，因此我們以50 %溶血程度為指標，觀察鎘對紅血球細胞膜強度之影響，結果顯示魚經低劑量 (0.6 mg/Kg) 鎘腹腔注射後，其溶血現象在各組間無顯著差異，但是以高劑量 (3 mg/Kg) 鎘腹腔注射48小時後，其溶血現象顯著低於對照組與注射生理食鹽水組，推論經鎘處理後之吳郭魚紅血球細胞膜有增強之作用。觀察鎘對魚淋巴球數量之影響，以 0.6 mg/Kg鎘處理與注射生理食鹽水組 (注射體積為5 ?L/g體重) 與空白組比較皆無顯著差異，但是經2 mg/Kg鎘處理與注射生理食鹽水之組 (注射體積為15 ?L/g體重) 皆顯著低於對照組，由於鎘處理組與注射生理食鹽水組，並無顯著差異，因此我們推論：使魚類之淋巴球數量減少的原因，可能是注射時間 (或量) 過度所引起之緊迫。

The aim of this study is to compare the haemolysis and lymphocyte numbers in Tilapia to cadmium injection (treatment), saline injection (control) and blank treatment. A linear relationship of haemolysis is observed when erythrocyte is exposed to 0.24%-0.32% saline. Haemolysis and lymphocyte numbers do not exhibit any significant difference between low dose (0.6 mg/Kg Cd2+) treatment, and control and blank groups. However, the levels of haemolysis are found to decrease at a higher dose (3 mg/Kg Cd2+) of treatment compared to the control and blank groups. We suggest that Cd2+ might induce a higher tolerance to hypotonic solution in erythrocyte. In addition, lymphocyte numbers do not exhibit a significant difference between the treatment, control and blank groups except, when Tilapia is injected with 2 mg/Kg Cd2+ and 15 ?l/g saline. In this case, the numbers of lymphocytes found in the treatment and control groups are significantly lower than in the blank. Therefore we suggest that stress might decrease lymphocyte numbers in fish.