Accumulation and excretion of 95Zr and 95Nb by common goby (Acanthogobium flavimanus)

In order to gain more information of 95Zr and 95Nb accumulation and excretion by marine fish, a laboratory study was undertaken using common goby. Radioactivity of 95Zr and 95Nb in the tissues or organs was simultaneously measured and readily distinguished by a high resolution detector, Ge(Li). More than 60% of both total body burden of 95Zr and 95Nb was concentrated in the viscera (mainly digestive tracts) in spite of the small weight per cent (1.3%). The concentration factors of 95Zr and 95Nb on the 14th day after exposure were 34 and 42 for viscera; however, those were estimated to reach 70 and 83, respectively, if the fish were reared for a month under a constant level of radioactivity in sea water. The turnover rate of viscera was 0.0081 for 95Zr and 0.0018 for 95Nb, and the biological half time was 85 days for 95Zr and 385 days for 95Nb, respectively. In an elution pattern by gel filtration (Sephadex G-75) for viscera of common goby labelled by 95Nb, more than 80% of the total activity in the extracted solution exists with a relatively large molecular weight protein (probably more than 35,000). Although, 95Nb probably has no biological function in fish, it was apparently found to be organically bound in viscera of the fish. (author)