Dr. L. R. Donaldson, Director Applied Fisheries Laboratory Uni sity of Washington Seatcvle 5, Washington December 11, 1956 Comments on gr 79 in Land Crabs re.: Dr. Seymour's letter of December 4, 1956: The Sr?° levels in. land crabs can be expected to remain constant (excepting physical decay) over a period of years. This statement is basedon the data resulting from repeated. collections at Belle Island, Eniwetok, during a period of two years following Nectar test. . The radioactivity in the carapace (exoskeleton) due to long lived isotopes remained approximately constant at a level of approximately 10,000 d/mn/e wet throughout a period of 23 | months during which collections were made. Radiochemical analysis of 15 samples taken at various times during the collecting period, and three samples taken 35 days before Nectar test demonstrated that virtually 100% of the long lived isotopes was Sr?” and its ¥9° daughter. The land crabs being omnivorous can probably be considered an index of biologically available strontium. However, the ratio of the strontium to that’ in food items is not known.—~ Judging from the meager data presently available the radiostrontium content of the crab skeleton is more than ten times that in land plants on a -wet weight basis and is more than three times that in soil on a dry weight basis. The data from the Belle Island collections indicates that turnover of strontium in the land crab skeleton is rapid. S0020b1 i The —