Histological based sub-chronic toxicity testing of target heavy metals in fresh water; Using the Histo-morphometry of Kidney of Coptodon Zilli

This histology based toxicological study is aimed to advance the histopathological characteristics of fish kidney exposed to some known crude oil spill heavy metals. 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 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. Quality histologically results showed alteration which were consistent with heavy metal exposure studies. Semi-quantitative assessment showed significant difference between control and experimental kidney organ histopathological indices. The study further validates MATC fresh water guideline use for toxicity certification in Cr, Cd and Ni exposure.