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PACIFIC SCIENCE, Vol. XXI, April 1967 
intermolt value was calculated to be 19.80% 
of the dry weight. Analysis of variance illus- 
trated that there were no significant differences 
among the means. However, there is a sug- 
gestion that the gills may store phosphorus 
during the D x _ 2 stages. This suggestion is 
reinforced by the gill organic content at D 4 _ 2 
(Figure 2). The phosphorus content may be 
indicative of an energy-requiring process for 
early postecdysial absorption of sea water. 
Figure 6 demonstrates the alterations of 
calcium and phosphorus content of the muscle 
throughout the molt cycle. The calcium con- 
centration increased from 7.70% at the C 3 _ 4 
period to 10.72% at the D 3 _ 4 stage. Following 
ecdysis the calcium content was reduced to 
4.14%, and at the B 4 _ 2 period it was further 
reduced to a significant 2.72%. During the 
period when the majority of calcification oc- 
curred (between B 4 . 2 and C 4 . 2 ), the muscle 
calcium was raised to 6.28%. 
During the process of exuviation, i.e., the 
time when active musclar contractions occur 
to facilitate withdrawal of the crab from the 
old exoskeleton, a large amount of energy 
would be required. As can be seen in Figure 2, 
the organic content of this organ also increased. 
Another requirement would be an ample supply 
of calcium to expedite muscular contractions. 
Calcium and organic reserves may be localized 
in this organ to insure proper exuviation. This 
phenomenon would then favor the survival of 
the crab during the process of ecdysis. The 
muscles, in addition to the mid-gut gland, may 
also serve as a place for calcium storage. 
The 6.58% decrease in calcium between 
the D 3 . 4 and A 4 . 2 periods may be due to the 
mobilization of the element to the exocuticle; 
during the first postecdysial stages, the latter 
is impregnated with and concomitantly hard- 
ened by calcium salts (Travis, I960, 1963). 
The muscle phosphorus content was greater 
than that of calcium; phosphorus is the most 
important element in muscle contraction. The 
values at D 4 . 2 (25.98%) and A 4 . 2 (24.82%) 
were significantly different from the intermolt 
content of 13.14%, but the former values were 
not statistically different from each other. The 
loss of phosphorus during D 3 „ 4 may have been 
due, in part, to the mobilization to the gills and 
carapace, but 2.67% cannot be accounted for. 
The reasons discussed in the above paragraph 
seem to be applicable to phosphorus as well as 
to calcium. However, the suggestion that pro- 
ecdysial storage of phosphorus in the muscles 
occurred is indeed very weak. 
On examination of Figure 6, it can be seen 
that phosphorus and calcium are controlled 
differently. After ecdysis the amount of calcium 
in the muscles is diminished, but the phos- 
phorus content remains relatively constant. 
The phosphorus and calcium fluctuations in 
the digestive gland are seen in Figure 7. As 
found in the alterations in carapace calcium and 
phosphorus (Fig. 4), the curves tend to be 
reciprocal to each other. But the mid-gut gland 
phosphorus content was always greater than 
that of calcium. Significant differences among 
the means did exist (P < 0.01). 
The intermolt calcium content of 9.31% 
did not differ significantly from that at D 3 _ 4 
(13.05%). However, the gain suggests that 
some calcium is stored in the mid-gut gland 
during premolt. After ecdysis some of the cal- 
cium (5% in P. vigil ) may be used for cal- 
cification of the exocuticle. These observations 
are consistent with the reports of Paul and 
Sharpe (1916), von Schonborn (1912), Drach 
(1939), Kincaid and Scheer (1952), and 
Travis (1955^), but are inconsistent with that 
of Robertson (I960), who reported that in 
C. maenas the mid-gut gland secretion during 
postmolt (stages A and B) had about 16% 
more calcium than it did during intermolt. 
The phosphorus content decreased from 
19.76% in C 3 _ 4 to 15.28% in the late D stages 
and increased to 21.04% and 25.50% during 
the A t _ 2 and B 4 . 2 stages, respectively. The 
postecdysial gain may have been due to mobili- 
zation from the gills (Fig. 5), which lost ap- 
proximately 10% during postmolt. It is obvious 
that this gland in P. vigil does not store phos- 
phorus during the premolt periods, but it does 
appear that the gland becomes a phosphorus 
reservoir after ecdysis. This finding is incon- 
sistent with the reports by Travis (1955 b, 
1957) that phosphorus was stored in the mid- 
gut gland of P. argus prior to ecdysis, but that 
following molt, the phosphorus content rapidly 
decreased. The latter conclusion was based 
primarily on histochemical observations and 
