Haemogram of adult Clarias gariepinus exposed to chronic levels of roundup
Clarias gariepinus (mean weight, 850 ± 60 g) mean length, 38.75 ± 6.7 cm) were exposed individually to four concentrations of Roundup, containing 360g/l glyphosate in the form of 480g/l isopropylamine salt (1.5, 3.0, 4.5 and 6.0 mg/l) and a control (0 mg/l), five replicates per concentration for 70 days in static renewal boassay to determine the effect of exposure on selected blood variables (red blood cells, RBC; packed cell volume, PCV; white blood cell (WBC). thrombocytes, reticulocytes absolute red cell indices- mean corpuscular volume (MCV), mean corpuscular haemoglobin (MCH) and mean corpuscular haemoglobin concentration (MCHC), leucocrit. Exposure to chronic levels of Roundup caused a reduction in the values of PCV, HB, ESR, thrombocytes, WBC, reticulocytes, RBC, MCV and MCH relative to the control. Response o the blood variablesamong the treated group varied very widely and was not directly related to concentration of herbicide except in thrombocytes. There was a reduction in the values of the variables involved in oxygen transport (PCV, Hb, RBC) and absolute red cel values in some of the exposed fish. Thrombocytes appeared to be the most responsive variable as the value was drastically reduced from 1060 x 109 cells/l at 1.50 mg/l to 122.50 x 109 cells/l at 6.0 mg/l. It was only in the ESR that the value in the control (0.25 mmhr-1) was significantly different from that of the treated groups (6.0 mmhr-1 at 6.0 mg/l). The regression lines of best fit for the relationship between the herbicide concentration and the various variables showed that the responses of the test fish to the herbicide varied as indicatedby the curve types. The response of adult C. gariepinus to subethal concentrations of Roundup suggest that the fish could be under ntense physiological stress in the wild and culture conditions where the herbicide is applied at the recommended rate (liquid, 12l/ha; solid, 2.2 kg/ha) without the least effort to maintain the maximum recommended 0.6 mg/l in 1m water column after application.