Land Crabs and Fission Products at Eniwetok Atoll 1 
Edward E. Held 2 
Periodic studies of the effects of the atomic 
testing program on the biota of the Marshall 
Islands have been made since 1946 by the staff 
of the Applied Fisheries Laboratory, University 
of Washington (Biddulph and Cory, 1953; Don- 
aldson et al., 1948, 1949, 1956; Palumbo, 1955; 
Seymour et al., 1957; AEC reports UWFL-7, 
-16, -19, -23, -33, -42, -43). During the testing 
program at Eniwetok in 1954 a continuous bio- 
logical survey was initiated. In this report the 
portion of the survey concerned with the uptake 
of radionuclides by the land hermit crab, Coeno- 
bita perlatus Edw. T., 3 is presented. Results of 
possible 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 
available radiostrontium in the environment. 
Coenobita is an omnivorous scavenger which 
feeds primarily on land plants and on detritus 
washed up on the beaches. It is primarily noc- 
turnal and spends the daylight hours hidden in 
shrubs or under debris. 
The crabs were taken from Belle Island 
(Bogombogo) which lies 2.3 nautical miles 
southwest of the site of the Mike test of 1952 
and the Nectar test of 1954. This island is down- 
wind from the site of these tests. 
Prior to the Mike test Belle Island had a 
covering of shrubs, coconut palms, and trees 
(Palumbo, MS). The island was denuded by 
the blast in November 1952, but by April 1954 
it had regained a heavy growth of shrubs, prin- 
1 Contribution from the Laboratory of Radiation 
Biology, University of Washington, under Contract 
No. AT (45-1 ) 540 with the United States Atomic 
Energy Commission. Manuscript received March 31, 
1958. 
2 Laboratory of Radiation Biology, University of 
Washington, Seattle. 
3 We are grateful to Dr. C. H. Edmondson, Bernice 
P. Bishop Museum, Honolulu, Hawaii, for identifica- 
tion of the species. 
cipally Scaevola frutescens and Messers chmidia 
argentea. The regrowth was from seedlings and 
stumps of old plants. A rookery of fairy and 
noddy terns had also become established. Belle 
Island was again denuded by the Nectar test of 
May 1954: save for stumps and some stripped 
branches. Dead birds and fish were found in the 
center of the island as well as along the shores. 
One dead Coenobita was found, but almost all 
of a population of about 50 in one pile of debris 
survived, probably because of the protection of 
the debris and their habit of quickly withdraw- 
ing into their shell when disturbed. It is prob- 
able that they withdrew at the first flash of 
light before the blast reached them. 
Belle Island regained a lush cover of shrubs 
by August of 1954, less than three months after 
the Nectar test, and a fairy tern egg found three 
months later, in late November, marked the 
beginning of a new rookery on the island. 
ACKNOWLEDGMENTS 
The wholehearted cooperation of all members 
of the staff of the Applied Fisheries Laboratory, 
who at various times participated in the col- 
lection and preparation of samples, made this 
report possible. Miss Dorothy J. South supplied 
the results of the radiocesium, radiocerium, and 
some radiostrontium determinations. The co- 
operation of the U. S. Atomic Energy Commis- 
sion Division of Biology and Medicine and the 
Eniwetok Field Office, Task Group 7.1, and 
Holmes and Narver greatly facilitated the field 
collecting. 
METHODS 
Collections were made at approximately daily 
intervals commencing with the third day follow- 
ing Nectar until the ninth day. Thereafter, the 
interval between collections was progressively 
lengthened to approximately monthly intervals. 
Three crabs were taken at each collection except 
that in three instances five, and in one instance, 
only two were taken. 
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