Accumulation and transport behaviour of <sup>241</sup>americium, <sup>60</sup>cobalt and <sup>134</sup>cesium by eggs of the spotted dogfish Scyliorhinus canicula

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Journal Article
Marine Pollution Bulletin, 2007, 54 (7), pp. 912 - 920
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An experimental study examined the 96-h net influx from seawater of the anthropogenic radionuclides 241Am, 60Co and 134Cs through the egg-case of the spotted dogfish Scyliorhinus canicula. Net influx directly through the wall of the egg-case was greatest for 134Cs, then 241Am and lastly 60Co. Within the egg-case wall itself the measured concentration factors (CFs) and their gradients in the external, median and internal layers showed that for both 241Am and 60Co they were >103 in the external layer and declined by an order of magnitude in the interior layer. In contrast 134Cs had a CF of only about three in the external layer which declined by a factor of 2 towards the two more internal layers of the egg-case. The egg-case apertures, that open within the prehatching stage of embryological development, significantly (P < 0.05) increased the net influx of 241Am and 60Co to the interior of the egg-case, although their water concentrations were still lower than those in the labelled seawater bath. In contrast, the aperture did not increase the net influx of 134Cs whose water concentrations equilibrated with those in seawater. Together these results indicate that the egg-case wall is very permeable to 134Cs, representing little barrier to its movement, and hence consistent with the lack of importance of the aperture in determining its internal water concentrations in the egg-case. In contrast, 241Am and 60Co show much higher rates of accumulation by the egg-case, consistent with the measured reduced permeability of its wall, and therefore giving greater prominence to its aperture in the net transfer of these two radionuclides to the egg case's interior. The presence of the embryo within its egg-case did not significantly (P > 0.05) affect the rates of influx of radioisotopes, with the exception of an interactive effect for 60Co with the egg-case aperture (P < 0.05). The CF of only 241Am in the embryo itself relative to the external seawater concentration was significantly (P < 0.05) enhanced by the presence of the aperture. © 2007 Elsevier Ltd. All rights reserved.
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