Metabolism of radionuclides in a cephalopod, Iidako, Octopus ocellatus

Retention, distribution and excretion of radionuclides in a cephalopod, Iidako, Octopus ocellatus, were observed by administering radioisotopes (54Mn-, 59Fe-, 60Co-, 65Zn-chlorides and 57Co-cyanocobalamin) into the mantle cavity by injection. Whole body radioacti vity of the octopus was measured periodically after the injection for one to ten weeks to obtain t he retention curve. At different stages after the injection, the sacrificed octopus was dissected into eight parts to examine the distribution of radionuclides and its change with the lapse of time. For some organs of the octopus, gel filtration chromatography (GFC) with Sephadex G-75 was applied to elucidate the binding of radionuclides with the constituents of the octopus. Excretion patterns consisted of two or three components for every nuclides except 57Co-cyanocobalamin which showed monophasic elimination. 54Mn was lost most rapidly whereas the longest biological half-life was shown by 59Fe. The most significant distribution of radioactivity was observed for sup(57,60)Co and 59Fe in the branchial heart of the octopus, while no specific accumulation of 54Mn and 65Zn was shown in this organ. The different accumulation mechanisms between each chemical form of cobalt and among the nuclides were suggested from the GFC elution profiles of radioactivity in the branchial heart and the liver. (author)