237Pu experiments with the thornback ray Raja clavata

Some experiments have been made on the metabolism of ²³⁷Pu — a high specific activity, gamma-emitting isotope of plutonium — by the thornback ray Raja clavata L. Unlike previous experiments with the plaice (Pleuronectes platessa L.) it was found that the thornback ray absorbed plutonium across the gut wall, as readily observed by analysis of the liver. The liver accumulated up to 0.2% of the ²³⁷Pu given in a single labelled meal after a period of 12 days. Direct injection of the isotope into the muscle of thornback rays resulted in extremely slow rates of elimination from the fish, the highest internal concentrations being attained by the spleen. The largest fractions of the whole-body burden, however, were those of liver and skeleton.