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Biokinetics of cadmium and zinc accumulation and depuration at different stages in the life cycle of the cuttlefish Sepia officinalis
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Edité par CCSD ; Inter Research -
International audience. Bioaccumulation of 109Cd and 65Zn by the cuttlefish Sepia officinalis was studied at different stages of its life cycle, i.e. in embryos, juveniles and adults, following exposures via sea water, sediments and food. Cuttlefish eggs efficiently accumulated both elements from sea water with bioconcentration factors reaching 46 for 109Cd and 79 for 65Zn after 11 days of exposure. Most of the radiotracers was found in the capsule membrane of the eggs, demonstrating that the capsule acts as a shield to protect embryos against metals. Juveniles and adults efficiently bioconcentrated both radiotracers from sea water, with the muscular tissues containing 62% of the total 109Cd and 84% of the total 65Zn. Loss kinetics followed a single exponential function for 65Zn while for 109Cd, loss was best described by a double exponential model. Biological half-lives for elimination were ca. 2 months for both elements. After 29 days of depuration in uncontaminated sea water, 76 to 87% of the radiotracers were found in the digestive gland. For both elements the dissolved phase can be considered as a significant source of accumulation. In an experiment with radiolabelled sediments, transfer factors were very low, even after 29 days of exposure. Food chain transfer experiments demonstrated that both juveniles and adults assimilated 109Cd and 65Zn very efficiently. Moreover, loss of ingested radiotracers was much slower than elimination of 109Cd and 65Zn taken up from sea water, indicating a very strong retention of dietary Cd and Zn by juvenile as well as by adult cuttlefish. As with direct uptake from sea water, ingested radiotracers were mainly found in the digestive gland with fractions reaching 82% for 65Zn and 97% for 109Cd after 29 days of depuration. These tracer experiments indicate that (1) food is likely the primary pathway for Cd and Zn bioaccumulation in Sepia officinalis and (2) the digestive gland plays a major role in the subsequent storage and presumed detoxification of these elements regardless of the uptake pathway.
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