Tissue elemental status of the freshwater clam, Galatea paradoxa (donacidae) from the cross river, Nigeria

The soft tissue levels of six nutritional elements [Magnesium (Mg), Calcium (Ca), Iron (Fe), Copper (Cu), Zinc (Zn), Manganese (Mn)] and two toxic elements [Lead (Pb), Cadmium (Cd)], were determined in the freshwater clam, Galatea paradoxa from the lower Cross River, Nigeria. The dominant element was Mg which accounted for 69.97% of total tissue elemental concentration. This was followed by Ca (12.97%), Fe (10.53%), Cu (7.19%), Zn (5.56%) and Mn (2.72%). Both Pb and Cd constituted < 1% of the total elemental content. The concentrations of Mg, Ca, Pb and Cd increased with clam age while those of Fe and Mn decreased. Variations in the concentrations of Cu and Zn were age‐independent.

Clams stored in demineralized water over a 5‐day period exhibited a decline of tissue elemental contents. The toxic elements (Pb, Cd) were most heavily lost on the first day and the majority of the essential nutritional elements, between the second and third days. It is conjectured that the consumer can reduce the toxicological impacts of Pb and Cd by depuration over a minimum duration of one day. However, for optimum, consumer nutritional benefit from the essential elements, depuration should not exceed two days.

Key words:

• Galatea paradoxa
• nutritional and toxic elements
• ecotoxicity
• storage
• depuration

Notes

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