Abstract:
The toxicity of Jatropha curcas (0, 133.3, 200, 266.7, 333.3 and 400mg/l) to the fingerlings and adults of two economically and most widely cultured fishes, Clarias gariepinus and Oreochromis niloticus were studied under static bioassay to determine its acute toxicity under laboratory conditions over a 96hour exposure period. The 96h LC50 of J. curcas to adults and fingerlings of C. gariepinus were 306.5mg/l and 402.7mg/l, respectively while that of O. niloticus adult and fingerlings were 229.1mg/l and 402.7mg/l, respectively. Both fishes exhibited clinical signs such as air gulping, loss of reflex and erratic swimming prior to mortality. Haematological examination of adult C. gariepinus showed an increase in Red blood cell (RBC), Packed cell volume (PCV), Haemoglobin (Hb), Mean corpuscular haemoglobin (MCH) and Mean corpuscular volume (MCV) values, while there was a reduction in the White blood cell (RBC). The Mean cell haemoglobin concentration (MCHC) values were similar to those in the control treatment; while in the fingerlings, the PCV, Hb, MCHC, WBC and MCV values increased and there was a reduction in the RBC and MCH. In adult O. niloticus haematological examination showed a decrease in most of the parameters ; WBC, RBC, PCV, Hb and MCHC. This was similarly observed for the fingerlings, except MCHC, in which there was no significant difference (p>0.05) but there was an increase in MCV. Mortality increased with increase in concentration of J. curcas and with time of exposure in the fingerlings and adults of both C. gariepinus and O. niloticus. Results indicated that J. curcas seed powder did not have adverse effects on water quality. The histological examination of the gill, liver and skin of both O niloticus and C. gariepinus showed lesions which increased progressively with increasing levels of the toxicants. In the gills, filament cells showed lesion, necrosis, stunted lamellae, cellular degeneration and erosion. In the liver; there was vacuolar degeneration, portal congestion and hepatic vacuolar degeneration while in the skin there was mild lesion, necrosis, diffuse myofiber disintegration and cellular infilteration by monocular cells. The results of this study revealed that J. curcas seed powder has piscicidal property. The result also provide a baseline information and established safe limit of using J. curcas seed powder in fresh water ponds.
