Cadmium (Cd) influences calcium (Ca) levels in the skeleton of a freshwater fish Channa gachua

Environmental contamination with heavy metals is a threat to the organisms due to their toxicity, persistence and bioaccumulation in food chains. The study was aimed to assess cadmium (Cd) effect on calcium (Ca) level in bones of a freshwater fish Channa gachua. 42 fish individuals were kept into six (6) aquaria; labelled aq.0, 1, 2, 3,4 and 5 in the laboratory for treatment. Aq.0 was control group and aq.1, 2,3,4,5 were experimental with treatment solution of Cd 0, 0.1ppm, 0.5ppm, 1ppm, 2.5ppm and 5ppm respectively for three months. After exposure, bones tissue were examined for Cd accumulation and Ca concentration. Highest accumulation of Cd were recorded in aq.5 mean 46.86 ± 0.46 mgkg-1 .and lowest in the control group with mean 0.61 ± 0.06 mgkg-1. The order of Cd bioaccumulation in bones were aq.5 > aq.4 >aq.3 > aq.2 > aq.1 > aq.0. Highest concentration of Ca were noted in aq.0 (Control group) mean 7888.06 ± 4827.22 mgkg-1 and lowest were 1132.36 ± 203.73 mgkg-1 in aq.5 (at 5.0 ppm). Generally a pattern of decreasing Ca level were observed with each rise of Cd bioaccumulation aq.0 > aq.1 > aq.2 > aq.3 > aq.4 > aq.5. Current study indicated that Cd accumulation have substantial effect on Ca level in bones and hence on skeleton system. Strict rules must be implemented by government to control metals pollution and exploitations of biota.