AOS aay
PRELIMINARY TEST OF RADIOACTIVITY IN COCONUT CRABS AT ENIWETOK ATOLL
COLLECTED IN 1972
PROCEDURE
Samples of skeleton and muscle from two specimens of coconut crabs (Birgus
Jatro L.) collected on 21,January 1972, Glenn Islet, Eniwetok were dried,
pulverized and placed in liquid scintillation vials with Insta-Gel as a
suspending and scintillation medium.
These samples were compared with similar
tissues from the crab Pachygrapus crassipes collected near Laguna Beach,
California in June 1972.
These latter specimens are assumed to not contain
significant amount of radioactive nucleides.
Table | gives a description of
the samples.
Samples were compared using a Packard Series 2000 Liquid Scintillation
Spectrometer.
For total radioactivity a window of 50 (on a 1000 maximum scale)
to infinity was used, using the 20, 60, and 80% gain values of the instrument.
For characterization of the spectrum a 10% window width (50-150) was employed
at various gain teveis.
RESULTS
Preliminary tests indicated that there is definite excess of radioactivity in
the coconut crabs for Eniwetok.
However, it is so small that considerable
amounts of sample had to be used to permit detection and characterization of
the spectral distribution.
Tests on the total count are reported in Table !.
Analysis of this data also
gives considerable evidence of quenching as the weight of the sample used
increases.
This was tested further (following spectrum analysis) by adding
a standard amount of 43cq to each tube.
The increase in counts was
inversely
proportional to the size of the sample.
Quenching (in sample 5) was noted to
be less pronounced (23% decrease) when a hicher energy nucleide (29s) vias
added as compared to a weaker nucleide (153) which showed a 66% decrease. ~
Scintillation vials without any crab tissue present but with a standard
amount o
5 90 Sr
or
4s Ca
were used for comparison.
y
-