EFFECT OF CADMIUM TOXICITY ON GROWTH AND SOME PHYSIOLOGICAL PARAMETERS OF NILE TILAPIA (OREOCHROMIS NILOTICUS)

EFFECT OF CADMIUM TOXICITY ON GROWTH AND SOME PHYSIOLOGICAL PARAMETERS OF NILE TILAPIA (OREOCHROMIS NILOTICUS)

Mohamed Wafeek

Department of Fish Physiology and spawning, Central Laboratory for Aquaculture Research, Abbassa, Abo-Hammad, Sharkia, Egypt.

Abstract

The effect of waterborne cadmium (Cd) toxicity on growth performance, some physiological parameters, and Cd distribution in different organs of Nile tilapia, Oreochromis niloticus (L.), was investigated. Fish (45.3±0.7 g) was randomly distributed at a rate of 10 fish per 120-L aquarium and exposed to 0.0 (control), 0.56 (T1), or 1.12 (T2) mg Cd/L for 8 weeks in triplicates. Fish growth performance decreased significantly with increasing Cd concentrations; however, the lowest fish growth was observed at T2. Moreover, Cd-exposed fish consumed less feed than the control fish group. It is also noticed that hemoglobin (Hb), red blood cells (RBCs), and hematocrite (Hct) decreased significantly with increasing Cd concentrations. The highest level of Hb, RBCs, and Hct were recorded in the control fish group. The activities of hepatic superoxide dismutase (SOD), catalaze (CAT), glutathione peroxidase (GSTp), and glutathione transferase (GSTt), increased significantly, while glutathione reductase (GSTr) decreased significantly with increasing Cd concentrations where the highest levels of SOD, CAT, GSTp, and GSTt were recorded in T2. Moreover, hepatic lactate dehydrogenase (LDH), phosphofructokinase (PFK), and creatine kinase (CK) activities increased significantly with increasing Cd concentrations. The lowest activities of LDH, PFK, and CK were recorded in the control fish group. Moreover, the highest glucose-6-phosphate dehydrogenase (G-6-PD) value was recorded in Cd-exposed fish and lowest value was showed in the control fish group. Cadmium residues in fish gills, liver, muscle, and whole-fish body increased significantly with increasing Cd concentrations. It is also noticed that the pattern of Cd accumulation in fish organs was in the order liver > kidney > gills > muscles.

Keywords: Cadmium, Nile tilapia, physiological parameters, Cd bioaccumulation, defense system.