Haematology, Oxidative Stress and Micronuclei Frequency of Clarias Gariepinus Exposed to Glyphosate based Herbicide Glycot® GBHG

Abstract

Glyphosate (N-phosphonomethyl glycine) is a broad-spectrum systemic herbicide used extensively in weed control in Nigeria. The present study was designed to evaluate the toxicity effects of glyphosate-Glycot® on post juveniles (50±1.96g; 22±1.2cm n=300) of Clarias gariepinus exposed to triplicate acute doses: 31, 33, 35, 37 and 39 mg glycot L-1 of clean water and to 8 day sub-acute doses: 3.39, 6, 78 and 16.95mgL-1 of the same, corresponding to 1 /10 LC50=3.39 mgl-1 , 1 /5 LC50=6.78 mgL-1 , ½ LC50=16.95 mgL-1 ’ A set of fish were also maintained simultaneously in water as the control (0.0 mg glycot /L of clean water), during the exposure periods. The 96 hours LC50 of the herbicide to the fish was determined at 33.39 mgL-1 which corresponds to 96h safety dose of 1 /100 LC50 = 0.35 mg/L. Blood samples were taken at intervals of day 1, 4 and 8 for assessment of micronucleus frequency, hematology and antioxidant enzymes. The hematological parameters were significantly reduced in the treated values of PCV and ranged from 20.00±0.19 – 23.33±0.55 %) below the value of 28.33±0.61% recorded in the control. Similarly, the red blood cells RBC, and haemoglobin HB recorded inhibited ranges of 8.58±0.21 - 9.10±0.03 x 106 mm3 below their elevated respective controls of 10.06±0.03 x 106 mm3 and 8.73±0.05 g/dL. However, the white blood cells WBC and platelets PL recorded elevated ranges of 12934.00±544.68 - 13700.00±485.72 x 103 mm3 and 15933.33±322.79 above their respective control values of 9466.66 0.09±96.86 x 103 mm3 and 15633.33±181.89. Catalase CAT was significantly (p<0.05) inhibited in treatments compared to control, and it ranged from the highest value of 0.74 umol mm-1 mg protein-1 in control to the lowest value of 0.21 umol mm-1 mg protein-1 in exposed group to 16.95 mg/L on day 4 but returned to control value on day 8 in all the treatments. Superoxide dismutase SOD was significantly (p<0.05) inhibited among exposed fish compared to control on days 1-4. A range of 11.60 U mg protein -1 in control on day 1 to lowest value of 6.50 U mg protein -1 returned to control value on day 8. Similarly, GPX was significantly inhibited to a lowest value of 4.25 in fish exposed to 3.39 mg/L compared to the highest value of 9.36 in control fish on day 4 but returned to control value with a high value of 9.25 umol-1 min protein-1 . Similarly, Lipid peroxidation LPO ranged from the highest value of 6.8±0.00058 mMole/TBARS/ mg protein in 16.95mg/L to a lowest value of 6.41 mMole/TBARS/ mg protein in control on day 4, returned to the control value on day 8. The mean values of micronuclei frequency in the treatments were significantly (p<0.05) elevated above the control value of 8.50±0.93 to the highest value of 406.66±15.03. This finding indicated that GBHG impaired haematology, antioxidative stress enzymes and cytogenic potential of C. gariepinus and could serve as an early warning signs toward the avoidance of its ecotoxicological hazards in aquatic ecosystems in Nigeria