at TABLE VIII PERCENTAGE OF RADIOACTIVITY CONTRIBUTED BY DIFFERENT ISOTOPES IN TRIDACNA VISCERAL MASS AND KIDNEY, AND IN THE LIGHT AND HEAVY ‘ FRACTIONS OF THE KIDNEY Se Ru! —Rh!0s Zr®5__Nb® Mn*# 0 Cs?3?7__Ba!37m 0 0 0 Fe55 Co 57. 58, 60 0 11.6 0 6.0 ! 0 | Zr®5_Nb® Mn*4 C1057, 58, 60 | | | 3.6 0.5 8.7 87.0 0 Heavy fraction Light fraction °, of activity Bu%__Rpi0¢ 0 85.8 | Zn | i 0 | | Srs0__yso ae 2.2 0.3 0 | | | 72.0 22.0 Ce144__prl44 : _ Tridacna kidney o” of activity | | ae | Tridacna visceral mass | % of activity | | w % of activity 1 ! 0.3 0.04 16.4 83.0 In the visceral mass only 6°% of the total radioactivity was from Co%?. 58, 60, Ru?6— Rhl06 (72°) and Zr®5—Nb%5 (22%) accounted for the major part of the activity. The deposition of radioisotopes in the concretions of the kidney was studied by separating the kidney into a light fraction and a heavy fraction through homogenization and centrifugation. The heavy fraction contained more concretions than the light fraction. In the heavy fraction, Mn5* contributed approximately twice as much and the radioactive anions Ru!®¢— Rh!6, Zr95— Nb®> one-tenth as much of the total radioactivity as they did in the light fraction. The deposition of radioactive cations in one organ and radioactive anions in another appears to be related to the metabolism and retention of stable sodium, potassium, calcium, magnesium, phosphate, bromide, and chloride in these organs. Metabolism of the heavy metals probably also exerts an effect on the deposition pattern of radioelements. The levels of stable elements in the organs tend to parallel those of the radioelements. Zn®> was found in Hippopus kidney but not in that of Tridacna. Stable zinc is present in Hippopus kidney at a level 17 times that in Tridacna kidney. Mn** contributed twice the percentage of the total radioactivity in the heavy fraction of Tridacna kidney as it did in the light fraction, and stable manganese was present in the heavy fraction at a level six times that in the light fraction. The amount of phosphate in the kidney fractionsparalleled the levels of manganese, which is probably stored in the concretions as a manganese-phosphate-protein complex. The tridacnid clams differ from those in which symbiosis does not occur in that almost none of the accumulated ions are lost to the environment 134 |