Calcium and Phosphorus Metabolism of P . vigil — Sather 
207 
clearly demonstrates that less calcium is re- 
sorbed from the exoskeleton as the crab in- 
creases in size. The calculated slope was found 
to be 0.082, which indicates an increase of 
approximately 82 jxg Ca/mg ash for each 
centimeter increase in breadth. The slope dif- 
fered significantly from 0 (P < 0.001). A 
similar analysis was performed, comparing the 
amount of carapace calcium with the wet weight 
of the C 4 crabs. The results, which are not 
illustrated in this report, demonstrated that 
regression did not occur and that the calculated 
slope was 0.0009. Thus it appears that less cal- 
cium is resorbed by large crabs and, therefore, 
more calcium appears in the exuvia. This phe- 
nomenon illustrates the effects of ageing on 
one physiological process of an invertebrate. It 
may be possible that the enzymatic activities 
responsible for crustacean decalcification are 
decreased with age and those required for 
recalcification are not influenced by senescence. 
A study of the alkaline phosphatase and car- 
bonic anhydrase activities of the epidermal cells 
may verify the above observations. 
ACKNOWLEDGMENTS 
The author is grateful to Dr. Sidney J. 
Townsley of the University of Hawaii for his 
suggestions, encouragement, and guidance dur- 
ing the study. I wish to thank also Dr. Pieter 
B. van Weel and Dr. Terence A. Rogers, of 
the University of Hawaii, for their criticisms 
and assistance during the preparation of the 
manuscript. This investigation was financed, in 
part, by the U. S. Atomic Energy Commission, 
Contract No. AT( 04-3) -235. Portions of the 
manuscript were taken from my Ph.D. dis- 
sertation for the University of Hawaii. 
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