Haematoxicity, condition and organ indices of Heterobranchus bidorsalis treated with cymbush under laboratory conditions

Abstract

Heterobranchus bidorsalis (mean length 31.50 ± 2.32 cm SD; mean weight 241.25 ± 30.39 g SD) were exposed to cypermethrin (5.00, 7.50, 10.00, 12.50 and 15.00 ppb) and a control (0.00 ppb) for 23 days. Fulton’s condition was assessed at the beginning and end of the experiment. Organ (liver, kidney, heart and spleen) indices and haematological variables: packed cell volume (PCV) haemoglobin, Hb; leucocrit, erythrocyte sedimentation rate (ESR) white blood cells (WBC) thrombocytes, red blood cells (RBC) and their indices-Mean corpuscular haemoglobin, MCH; Mean corpuscular hemoglobin concentration (MCHC) and mean corpuscular volume (MCV) were determined. The haematological responses to the cymbush exposure were very variable relative to the exposure concentrations. However, there was a decline in the PCV, WBC and lymphocytes (P < 0.05) values in exposed fish compared to their control values. Highest decline in the blood variables, except in the value of lymphocytes occurred at 150 ppb. Hb, leucocrit, eosinophil and neutrophil values in exposed fish were very variable. Thrombocytosis was the most blood responsive variable (25 units at 150 ppb, above the control). ESR value was generally raised in the exposed fish compared with the control (1.75 ± 0.48 mm/hr). RBC indices (MCHC, MCH and MCV) in exposed fish did not vary (P ≥ 0.05) from the control. Fish condition generally declined from the initial values but final condition was raised above the control in almost all the concentrations (P > 0.05). The changes in the organ weights in exposed fish were variable except in the kidney. Results from this study indicate that exposure to sub lethal levels of cymbush impacted mainly on the blood variables with minimal changes in the condition and organ indices of the exposed fish. Hence, indiscriminate application of the insecticide should be checked to reduce contamination of the aquatic environment to the barest minimum.