Three pathways of exposure (sediment, seawater and food) were examined to determine transfer of 110mAg and 57Co in juvenile cuttlefish Sepia officinalis. Additional experiments were conducted on adult cuttlefish and their eggs/embryos in order to assess bioaccumulation patterns at different stages of the organism's life cycle. Eggs, juveniles and adults readily accumulated both Ag and Co from seawater. In eggs, both metals were predominantly adsorbed onto the capsule membrane (greater than or equal to60 % for Ag and greater than or equal to99 % for Co), indicating that the latter may act as an effective shield to limit exposure of embryos to soluble metals. Adult cuttlefish incorporated waterborne radiotracers mainly in their muscular tissues (greater than or equal to60 % of the whole-body burden); subsequent metal retention was greater for Co (biological half-life, Tb1/2 = 34 d) than for Ag (Tb1/2 = 7 d). Turnover of Co ingested with food was much more rapid in juveniles (Tb1/2 = 5 d) than in adults (Tb1/2 = 990 d), suggesting that the functional maturation of the digestive gland was not complete in the juveniles. With ingested Ag, retention was roughly similar for juveniles and adults (Tb1/2 = 13 and 9 d, respectively). Transfer from sediments was negligible for Co and Ag. Regardless of the exposure pathway, the digestive gland of juveniles and adults contained the major fraction of incorporated metal either following uptake or after depuration. This observation demonstrates that substantial metal transfer takes place from several organs to the digestive gland, and further highlights the major role this organ plays in metal storage and detoxification processes in these cephalopods. |
