Analysis of Achyranthes aspera leaf extract and environmental safety evaluation to non target Nile tilapia fish fingerlings, Oreochromis niloticus.

Abstract

Background: Although plant molluscicides are biodegradable and less toxic to higher animals, unregulated applications could affect other non target aquatic species. Eco toxicological studies are required to evaluate whether they are safe to those economically and ecologically important fish species. According to previous studies, Achyranthes aspera is a molluscicidal plant with LC90 of 96.5 mg/L and the current study is to investigate its toxic effect to Nile tilapia fish fingerlings, Oreochromis niloticus. Methods: Seven fish fingerlings were exposed to serial dilutions of A. aspera leaf aqueous extract for 96 hours in duplicate setup. Phytoconstituents were identified by GC-MS and lethal concentrations were determined by probit model. The NOAEC was determined by hypothesis testing on the survival data. Results: The respective piscicidal LC1, LC10 and LC50 values were 897.4, 1063.9 and 1310.74 mg/L. The NOAEC was 1100 mg/L (p>0.05). GC-MS analysis revealed 12 phytoconstituents including a monoterpene. Conclusion: The result shows that A. aspera is non toxic and hence is safe to Nile tilapia fish especially at its molluscicidal dose limit (96.5 mg/L LC90) corroborating to the plant’s target specific molluscicidal potential.