host condition, parasite interaction and metal accumulation in tilapia guineensis from iddo area of lagos lagoon, nigeria

this paper investigates host condition factor, parasite interaction and metal accumulation in tilapia guineesis and host-parasite system in iddo area of lagos lagoon, nigeria. eighty specimens of t. guineensis from the lagoon were caught and dissected for intestinal helminth parasites. condition factors of all individuals were determined. median condition (k<2.62 and k>2.62) were used in grouping the individuals. sediment, water samples, livers and intestinal parasites were analyzed for heavy metals using atomic absorption spectrophotometer. metal concentrations in the water medium were below detectable limits, but those in sediments were; cadmium (cd) (mg/l), 11.29±22.59, manganese (mn)(mg/l), 0.02±0.02, iron (fe) (mg/l), 141.09±15.09, p<0.01, lead (pb))(mg/l), 123.16±8.41, p<0.01. livers of infested individuals accumulated more metals than those not infected by the parasites. this was also discovered when they were grouped based on their condition status. among the infested fish, high condition individuals (>2.62) accumulated more metals than the low condition infested individuals (<2.62), but irregular trend was found among the non-infested individuals. parasite prevalence among infested individual of low condition factor were; heterostomum sp., a trematode; 0.25, procamallanus sp., a nematode; 0.75, acanthogyrus tilapae , an acanthocephalan, 0.05 and proteocephalanus sp., a cestode was absent. high condition individuals had parasite load; heterostomum sp.; 0.45, procamallanus sp., 0.05, proteocephalanus sp., 0.05 and acanthogyrus sp.; 0.25. generally, the host liver accumulated more metals than their parasites except iron among parasites of high condition individuals. relative abundance and diversity in intestinal parasites with varying metal bioaccumulation potentials in high and low condition individuals could have been responsible for the difference in metal accumulation in their host tissue. therefore, it is recommended that environmental monitoring studies involving the use of fish could be improved upon by including the macro-parasites, considering the significant effect they could have in the fish biology, behaviour and ecology.