The dietborne metals in minute concentrations are essential for vital functions in fish. Fish diets may probably contaminated with some items as metals. Therefore, Nile tilapia (Oreochromis niloticus) is used to assess the toxic effects of contaminated diets with Cu, Cd or their mixture. Fish fed metals contaminated diet showed harmful alterations in its biological characters. The condition factor (K) was invariably reduced with significant differences (-28.86 % from the control value) for fish fed dietborne Cu for 30 days. Similarly, the hepatosomatic index (HSI) and gonadosomatic index (GSI) exhibited marked reduction. The total sarcoplasmic protein showed a mild reduction after 10 days of exposure to dietborne metals content, whereas, it was increased markedly as the duration prolonged to 20 to 30 days. It is worthy to mention that its maximal rise (66.87% above those of the control) was recorded after 30 days of exposure to Cu + Cd contaminated diet. Similarly, the total nitrogen content in the muscle of O. niloticus was obviously increased. Its maximal rise was 134.62% above those of the control value, resulted from high dietborne Cu for 30 days. Total protein content in plasma was significantly increased as induced by exposure to elevated dietborne Cu. This may possibly reflected certain degree of hepatocellular damage with a concomitant of its surge to the blood stream. Generally the total plasma albumin and globulin contents were generally increased due to high dietary Cu or Cd or Cu + Cd intake. The present study shows that the toxicity of Cu is higher than that of Cd. Nile tilapia (O. niloticus) fed on Cu contaminated diet for 10 days, exhibited sensitive proteins (last four fractions) were disappeared). On the other hand, Cd contaminated diet for 10 days induced one disappeared fractions (number 9). O. niloticus fed on Cu + Cd contaminated diet for 10 days, caused disappearance of the last fraction and others (7th and 8th) were faintly appeared. Thus, it could be mention that high dietborne intake of tested metals induced toxic effects of Nile tilapaia (O. niloticus).
Key words: Fish, Diet Contaminated Metals, Cu, Cd, Tilapia, Toxicity
|
