Bioaccumulation of heavy metals in Bothriocephalus acheilognathi cestoda and the definitive host, Cyprinus carpio (L. 1758)

Concentrations of three heavy metals as Manganese, Nickel, and Cobalt were estimated in two levels in the food chain; the omnivorous Cyprinus carpio fish and its intestinal cestode Bothriocephalus acheilognathi as end consumer (endoparasite) using atomic absorption technique. The study was performed in two locations in Tigris River, Al Rashedia and Sherikhan villages/Mosel City/ Nineveh Province between June 2022 to October 2022. The concentration of the three chosen metals: Mn, Ni, and Co, was estimated in the liver, gills, intestine, and skeletal muscles in both infected and uninfected fish and added to tissues of the cached Cestoda. Manganese concentration was the highest in the gills of both infected and uninfected fish 14.597, 21.773 µg/gm fresh weight, nickel concentration was the highest in the liver 4.44 and 8.10µg/gm fresh weight, and cobalt concentration was the highest in the intestine 2.467 and 7.79 µg/gm fresh weight. The difference in values was significant at P≤0.05 in the infected and uninfected fish, respectively. Accumulation of the three metals Mn, Ni, and Co was the lowest in fish skeletal muscles. Mn had the highest accumulation mean in fish organs 11.846 µg/gm fresh weight, Ni was the next 4.094 µg/gm, and Co was the lowest 2.616 µg/gm. The concentration of Mn and Ni in the cestode B. acheilognathi tissues 22.53 and 10.45 µg/gm was about two folds of that found in its host fish C. carpio. The concentration of Co was approximate in the worm tissues and its host fish. In conclusion heavy metals in C. carpio didn’t exceed the WHO and the FAO set permissible levels. B. acheilognathi cestoda could be a useful bioindicator for heavy metal contamination in aquatic ecosystems.