Table 4.9 RADIOACTIVITY OF ALL INVERTEBRATE SAMPLES COUNTED AT EACH COLLECTING STATION, POSTTEST® Maximum Minimum Average Japtan Igurin Rigili Bogallua Engebi Aaraanbiru’ Runit 0.47 0 0.083 15 0 4.0 400 0.35 44 7,700 25 1,200 15,000 10 1,700 6,800 2.1 1,100. 160 0.63 26 * Measured in disintegrations per minute per gram (x 1000), wet sample. rT a Sa 4. The digestive tract with its contents is usually the most radioactive portion. Its activity is highly variable, however, even within a species from the samestation. 5. Shell and carapace are also highly variable in specific activity. 6. The rankings of tisaues in descending order of specific activity with individual exceptions are as follows: a. Clams: (shell variable in position) (1) Digestive tract (visceral mass with contents) (2) Gill (3) Liver (4) Mantle (5) Muscle b. Snails: (1) Liver (2) Gill (3) Mantle (4) Muscle . Octopus (one specimen): (1) Liver (2) Gill (3) Muscle d. Hermit crabs: (carapace variable in position) (1) Digestive tract with contents (2) Liver (3) Gili (4) Muscle e. True crabs: (carapace variable in position) (1) Digestive tract with contents Ol Liver or gill (4) Muscle (c) Species Differences. There were not enough samples at any one island to reliably determine opecies differences. It is probable, however, that both species and individual differences are considerable, as is indicated by the data from the two similar species of sea cucumbers presented in Table 4.8. At Rigili and Igurin, where several specimens of crabs were taken (not more than two of one species), differences within a species are as great as between species. Tissue for tissue the land hermit crabs, Cenobita, may have a higher specific activity than the shore crabs. (d) Conclusions. The most obvious and striking conclusion is that there was great variability ia the amount of radioactivity found in invertebrates at every station sampled. The UNCLASSIFIE