Sublethal toxicity of cadmium chloride (CdCl2) on the growth parameters of Xenopus laevis tadpoles (Daudin, 1802)

Abstract

Intensive agricultural operations and industrial activities release enormous amount of heavy metals, such as cadmium into aquatic ecosystem. The degree of its toxicity indeed pose an environmental problem. The objective of the present work is to study the impact of sub lethal toxicity of waterborne Cadmium chloride for 8 weeks on the growth parameters of Xenopus laevis tadpoles. The research was carried out in the Fisheries Laboratory, Department of Biology, Ahmadu Bello University (ABU), Zaria, Nigeria. The tadpoles stage of development was gotten through artificial reproduction of adult Xenopus laevis collected from Ahmadu Bello University Reservoir. Some water chemistry such as temperature, pH, electrical conductivity, total dissolved solids and dissolved oxygen were monitored during the study. The tadpoles (Gosner stage 51) were exposed to Cadmium Chloride concentrations of 0.50, 1.00 and 1.50 mg/L derived from already established 96 h LC50, (8.86 mg/L CdCl2) in triplicates. The tadpoles were measured for growth parameters and the number that have completed metamorphosis were counted after an interval of two weeks for a period of eight weeks. Physicochemical parameters of water were within the normal range. The results of growth parameters of Xenopus laevis tadpoles showed that, the values of stages of development, Snout Vent Length (SVL), Hind Limb Length (HLL), Tail Length (TaL), Total Length (ToL), Live Weight Gain (LWG) and the percentage of tadpoles that completed metamorphosis of the exposed group of tadpoles decreased significantly (p< 0.05) compare with the controls. However, the decrease was concentration-dependent. The present basic information of the growth parameters would serve as a useful tool for further ecological assessment and monitoring of these aquatic organisms, which is considered to be an important food source for human beings and eco-toxicological tool in monitoring aquatic ecosystems in some parts of Nigerian.