Calcium and Phosphorus Metabolism of P. vigil — Sather 
205 
blood analysis, and no chemical analysis of the 
mid-gut gland was undertaken. 
A question arises after examining all of the 
phosphorus curves. Because the crabs were not 
feeding during the A and early B stages, where 
did the phosphorus originate? From Figure 5 
it is seen that the phosphorus content of the 
gills is drastically increased during the D 3 _ 4 
stages. Following ecdysis the phosphorus con- 
tent of the organ was reduced by approximately 
9%. The phosphorus content of the mid-gut 
gland from D 3 _ 4 to A t _ 2 was increased by about 
6%. Therefore, possibly the gills, rather than 
the mid-gut gland, serve as a phosphorus 
reservoir. Another possible source for the ac- 
cumulation of phosphorus could be the water 
that was imbibed immediately following ecdy- 
sis. However, this is not likely because a pilot 
experiment demonstrated that phosphorus is not 
accumulated during and following ecdysis. The 
application of the radioisotoype P 32 could be 
very useful in resolving this question. 
Figure 8 illustrates the calcium and phos- 
phorus contents of the blood during the molt 
cycle. The data are plotted on a volume basis, 
as is shown on the ordinate. The blood calcium 
and phosphorus levels tend to be parallel 
throughout the molt cycle. 
During the D 4 . 2 periods, the blood calcium 
was significantly increased to 35.09 mM/liter 
from the C 3 _ 4 content of 21.58. A significant 
decrease to 17.68 mM/liter was observed at the 
D 3 . 4 stages. In Panulirus argus , Travis (1955 b) 
also noted a premolt blood calcium increase, 
followed by a decrease in the late premolt 
stages. The loss was attributed to dilution when 
the lobster took in water. During the A period, 
the lobster’s blood calcium was at the intermolt 
value. The content was slightly increased at 
the B stages and, following this interval, i.e., 
during the C period, the concentration was de- 
creased below the intermolt value. In late 
premolt Carcinus maenas, Robertson (I960) 
also noted a blood calcium increase of about 
21%. Within 24 hours after molting (Stage 
A), the blood calcium content was reduced by 
approximately 25%. In 2 to 14 days following 
ecdysis, the blood calcium was further reduced 
to approximately 31% of the intermolt value. 
The water content of P. vigil decreases 
during proecdysis (Sather, 1966). Also, as 
evidenced from inspection of the changes in 
water content of sampled organs (Fig. 1), de- 
hydration definitely occurred during the pre- 
molt stages. The first decrease in water content 
was found during the D 4 _ 2 period. This would 
account for the rise in the blood calcium at this 
interval. The observed reduction at the D 3 _ 4 
stages is not due to the uptake of water. On a 
volume basis, the amount lost was calculated 
at 17.41%. However, on a dry weight basis, 
this loss was only 2.04%. The blood must 
have lost some calcium to other organs or the 
external medium. Thus, the calcium may have 
been distributed to the muscles and/or the mid- 
gut gland. The large standard errors (db 
1.2%) for the latter two organs do not permit 
an accurate estimate of the quantity accumu- 
lated by each organ. 
Following ecdysis, no significant changes in 
the blood calcium were observed. As seen in 
Figure 1, the greatest increase in water content 
occurred at this time. It should be recalled that 
the water taken in was sea water, including 
the elements present in the medium. This has 
been verified by the studies of Robertson 
(I960). Thus, a great calcium dilution would 
not be expected. Also, as seen in Figures 6 and 
7, the mid-gut gland and muscle lost some 
calcium which could have been accumulated 
by the blood. At period B^o the blood calcium 
was increased to 23.23 mM/liter. This could 
have been due to absorption of calcium, via 
the gills, from the environment. Figure 5 illus- 
trates that at this interval the gill calcium was 
drastically reduced, increasing the efficiency of 
extracting calcium from the external medium. 
Thus, except for the effect of dehydration at 
the early proecdysial stages, the calcium content 
of P. vigil blood remains more stable than in 
other investigated crustaceans. This fact may 
be due to the nearly chemically constant en- 
vironment of the crab. Except for one month, 
the environmental salinity and calcium was not 
less than 34 0/00 and 300 mg/liter, respec- 
tively (Sather, 1966). 
The total phosphorus fluctuations of the 
blood during the molt cycle are also depicted 
in Figure 8. The significant increase of blood 
phosphorus to the D^ interval of 25.52 mMI 
liter can be attributed to the desiccation of the 
animal. The reduction found at D 3 . 4 (17.19 
