TOXICITIES AND SEDATIVE EFFECTS OF TOLOACHE, DATURA INNOXIA MILLER, ON THE AFRICAN CATFISH CLARIAS GARIEPINUS BURCHELL, FINGERLINGS

Studies on toxicological and sedative effects of Datura innoxia plant parts (leaf, seed, stem, pod and root) on Clarias gariepinus fingerlings were conducted under laboratory conditions using the static bioassays and continuous aeration. The aim was to develop an effective anaesthetic from an indigenous plant material that will be available at low cost to aquaculturists and which would be non-toxic to the fish and consumers. The active ingredients and their compositions in the plant parts as well as their 96 hours acute toxicity (LC50) on C. gariepinus fingerlings were investigated. The effects of 12 weeks sublethal concentrations of the leaf, seed, stem, pod and root of the plant on growth, tissue composition, blood parameters, energy reserves, gills, gonad, kidney and liver of C. gariepinus were evaluated. Data obtained from this investigation were subjected to simple percentages and analysis of variance (ANOVA) at 0.05 level of significance. The phytochemical screening of the plant (D. innoxia) showed that the leaf, seed, stem, pod and root had alkaloids, atropine, hyoscyamine, scopolamine, flavonoids, essential oils, tannins and saponins. Similarly proximate analysis showed the presence of protein in all the five morphological parts examined. The Amino acid analysis indicated the presence of essential and non-essential amino acids at various levels in the leaf, seed, stem, pod and root. The D. innoxia water extracts resulted in a number of physiological impairment of C. gariepinus fingerlings. The mean LC50 range from 120.23 to 208.93 mg/l. Weight gain by C gariepinus exposed to sublethal concentrations of D. innoxia extracts ranged from 30.66 to 70.03%. Clarias gariepinus fingerlings exposed to various extracts of D. innoxia passed sequentially through the various stages of anaesthesia. The behavioural responses were excess mucus secretion and apathy, air gulping, distension of the mouth and opercula, erratic swimming and loss of balance. The crude extract of D. innoxia leaf was able to induce fish to loose reactivity to stimuli at concentration 2.50g/l within 40.33 (2.63) minutes, while at concentration 3.00g/l. the same effect was observed in 28.2 (2.06) minutes. No such observations were made at concentrations less than 2.50 g/l. Similar results were obtained from fish exposed to unseparated chloroform-methanol extract and lipid fraction of chloroform-methanol extract though the time taken to reach anaesthesia in the alcoholic extract was significantly (P < 0.05) shorter. The time required for C. gariepinus to succumb to the anaesthetic effects of the seed, stem, pod and root ranged from 1.04 (0.38) in the seed to 3.60 (1.08) minutes in the root for fish to loose reactivity to stimuli in unseparated chloroform-methanol and lipid fraction of chloroform-methanol extracts respectively. This study has shown that D. innoxia is a highly effective, cost efficient and safe anaesthetic for C. gariepinus use in aquaculture and laboratory research settings at concentrations not more than 3g/l.