Bioaccumulation of heavy metals and radionuclides from seawater by encased embryos of the spotted dogfish Scyliorhinus canicula

Encased embryos of spotted dogfish Scyliorhinus canicula absorbed six radio-isotopes (Am-241, Cd-109, Co-57, Cs-134, Mn-54 and Zn-65) directly from seawater during short-term experimental exposure, demonstrating the permeability of the egg-case to these contaminants. Embryo to water concentration factors (CFs) ranged from 0.14 for Cs-134 to 7.4 for Zn-65. The Zn-65 and Co-57 CFs increased exponentially with embryo length, whereas the CF for Cd-109 declined with length. Among different components of the encased embryo the egg case was the major repository (69-99%) of all six radio-isotopes that were distributed throughout its wall. Egg-case Us were as high as (103) for Co-57 and Zn-65, making it the major source of gamma radiation exposure to the embryo and potentially of radio-isotopes for continued absorption by the embryo, following the uptake phase of the experiment. The patterns of uptake by the egg-case approximated linearity for most isotopes and loss rates were isotope-specific; egg-case biokinetics were not greatly affected by the viability of the contained embryo. Within the embryo initial data on radio isotopic distribution show that the skin is their major site of uptake, as previously demonstrated for juveniles. (c) 2006 Elsevier Ltd. All rights reserved.