LAND CRABS AND RADIOACTIVE FALLOUT AT ENIWETOK ATOLL Introduction Periodic studies of the effects of the atomic testing program on the biota of the Marshall Islands have been made by the staff of the Applied Fisheries Laboratory, University of Washington, since 19462713 During the 1954 testing program at Eniwetok a continuous biological survey was initiated. In this rerort the portion of the survey concerned with the uptake of radionuclides by the land hermit crab, Coenobita perlatus Edw. Tt, is presented. Results of possitle ecological and physiological significance in the movement of strontium and cesium through the food cycle have been obtained. Strontium-90 concentration in the land crab skeleton may be a sensitive index of biologically aailable radiostrontium in the environment. Coenobita is an omnivorous scavenger which feeds primarily on land plants and on detritus washed up on the beaches. primarily nocturnal and spends the daylight hours It is hidden in shrubs or under debris. The crabs were taken from Belle (Bogombogo) Island which lies 2.3 nautical miles southwest of the site of the Mike test of 1952 and the Nectar test of 1954. This itsland is downwind from the site of these tests. Prior to the Mike test Belle Island had a covering of shrubs, * We are grateful to Dr. C.H. Edmondson, Bernice P. Bishop Museum, Honolulu, Hawaii, for identification of the species. ~1- pet