Gross anatomical based sub-chronic toxicity testing of target heavy metals using growth morphometrics of Coptodon zillii

This gross anatomical based toxicological study is aimed to assess the survival and growth rate juvenile Coptodon zillii exposed to potential target heavy metal from crude oil spill. Based on literature review on the environmental crude oil spill burdens of Niger Delta region of Nigeria , the following target chemicals (TC) were selected for the study: Cadmium (Cd), Chromium (Cr), Copper (Cu), Nickel (Ni) and Lead (Pb). The experimental type is a sub-chronicity fish exposure testing for twenty eight (28) days duration. The experimental set up involves a twenty two pieces (22) of twenty liter (20l) tanks of four (4) replicate tanks per target chemical (TC) containing ten(10) juvenile study fish per tank in a semi-static tank testing system. TC exposure concentrations above maximum allowable toxicant concentration (MATC) for fresh water were used for the study. At the end of the experiment survival and growth rate per tank of TC concentration is assessed. Results showed that survival rates were zero percent for TC concentration of Cu1, Cu2, Ni1, Ni2 and Pb2. There reduction in the relative growth rate (RGR) of fishes from exposed to the TC, except for fish exposed to TC concentrations of Ni4 and Pb3, where increase RGR was noticed. This study has shown that gross anatomical features of environmental bio-indicators can be used to validate MATC guideline concentration for fresh water ecological status.