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PACIFIC SCIENCE, Vol. XXI, April 1967 
mM/liter) possibly reflects the relocation of 
phosphorus to the gills (Fig. 5). At stage A^, 
the value was slightly greater than the intermolt 
value. This decrease can be assigned to dilution, 
i.e., by the uptake of water from the environ- 
ment. In sea water, phosphorus is present in 
much smaller quantities than is calcium. The 
annual average phosphate content of sea water 
was less than 1 pg/ liter (Sather, 1966). Also, 
the results of a preliminary experiment illus- 
trated that the phosphorus content of the ex- 
ternal medium was increased when containing 
molting and postmolt crabs. The leveling-off 
of the blood phosphate at B x . 2 and the increase 
at Q.o was probably due to the resumption of 
feeding. The majority of P. vigil began to feed 
at B 2 and only occasionally when they were in 
the B x stage. 
Ho mar us am eric anus (Hollett, 1943), Panu- 
lirus argus (Travis, 1955^), and Carcinus 
maenas (Robertson, I960) also increased their 
blood phosphorus during the premolt stages. 
Travis (1955 b) found that after ecdysis, the 
phosphorus content steadily decreased. This was 
attributed to a depletion of phosphorus by cal- 
cification of the exoskeleton concomitant with 
a reduction in the stored mid-gut gland phos- 
phorus. Robertson (I960) reported that within 
24 hours after ecdysis the blood phosphorus 
of C. maenas was slightly less than the inter- 
molt value. Within 2 to 14 days after molting 
the value was increased to about 22% above 
that of the intermolt level. The report of Dril- 
hon (1935) is not consistent with the above 
reports, in that the phosphorus content of the 
blood of premolt and postmolt Maia s quin ado 
was not altered. 
Composition of the Exuviae 
The discarded exoskeleton or exuvia of P. 
vigil is not consumed by the crab as it is in the 
insects. Robertson (1937) reported that the 
exuvia of Carcinus comprised about 46.2% 
of the total dry weight. Lafon (1948) stated 
that the value was 47.5% of the dry weight. 
These calculations were not made on the ex- 
uviae of P. vigil, but the percentages of organic, 
inorganic, calcium, and phosphorus contents 
were determined and these data are given in 
Figure 9. The per cent composition was based 
on the dry weight. The histogram illustrates 
that about 81% of the entire exuvia was com- 
posed of inorganic material and only approxi- 
mately 37% of the inorganic content was due 
to calcium. Odum (1957) reported that the 
calcium content of the exuviated chela of Uca 
pugnax was 27.7% of the dry weight, which 
is somewhat consistent with the calcium content 
of the exuvia of P. vigil. 
Knowing the amount of calcium in the 
exuvia (30%) and assuming that the intermolt 
carapace, which contained about 50% calcium, 
is representative of the entire exoskeleton, it is 
possible to calculate the quantity of calcium 
resorbed, which is about 20%. The amount of 
calcium stored in the mid-gut gland and the 
muscle was approximately 7%. Thus, the quan- 
tity stored and resorbed closely approximates 
the amount of calcium (26%) present in the 
early postmolt carapace. The increase in amount 
(23%) between A^ and C 3 . 4 undoubtedly is 
acquired from the environment. 
The phosphorus content of the exuvia was 
found to be only approximately 5 X 10“ 7 % 
of the dry weight. Unfortunately, comparable 
phosphorus data for other species have not been 
reported. Employing the above mathematical 
deductions, it would seem possible to account 
for the phosphorus budget. However, such a 
process produces a deficit of about seven magni- 
tudes. It is possible that the reproductive system 
and the gastrointestinal tract, which were not 
sampled, may have been highly selective for 
the storage of this element. The great resorp- 
tion of phosphorus is obvious and it must have 
been stored, because the results of an experi- 
ment showed that proecdysial and postecdysial 
crabs lose very little phosphate (2.6-5. 1 pg 
P0 4 ) to the environment. 
The organic content of the exuvia was found 
to be only 18.7%. This organic material has 
been reported to be composed of lipo-protein, 
chitin, mucopolysaccharides, and proteins (Tra- 
vis, 1955^, 1957, 1963; Dennell, I960). The 
amount of organic material resorbed was about 
17%, which is consistent with the amounts 
stored in the mid-gut gland and muscle. 
Neto (1943) reported that the calcium con- 
tent of the carapace of Uca maracoani decreased 
as its breadth increased. The calcium content 
of the exuviae of P. vigil was compared with 
the width of the cast exoskeletons. Figure 10 
