10 
PACIFIC SCIENCE, VoL XIV, January I960 
TABLE 2 
Number of Eggs per Mass of Different Sizes 
of Xanthid Crabs 
SPECIES 
CARA- 
PACE 
WIDTH 
EGGS 
COUNTED 
ESTI- 
MATED 
TOTAL 
L. 1. leucomanus 
8.5 mm. 
300 
1,250 
L. 1. leucomanus 
9.2 mm. 
300 
2,100 
L. 1. leucomanus 
10.0 mm. 
300 
1,000 
L. 1. leucomanus 
10.0 mm. 
300 
3,000 
L. 1. leucomanus 
1 1.5 mm. 
300 
3,600 
L. 1. leucomanus 
12.0 mm. 
300 
3,300 
L. 1. leucomanus 
12.5 mm. 
300 
3,500 
L. 1. leucomanus 
13.5 mm. 
300 
4,200 
P. taylori 
15.0 mm. 
300 
3,800 
P. taylori 
18.5 mm. 
300 
6,450 
P. taylori 
19.0 mm. 
300 
7,200 
P. taylori 
29-5 mm. 
300 
20,300 
C. novemdentatus 
32.9 mm. 
300 
22,500 
C. novemdentatus 
34.5 mm. 
300 
23,400 
C. novemdentatus 
38.5 mm. 
300 
40,680 
ever, the eggs are never stuck together after at- 
tachment, and are never attached to the ex- 
opodites, which are equally as "hairy” as the 
endopodites. Williamson (1903: 109) suggests 
that the endopodite "hairs” puncture each egg, 
and that the "umbilical” thread is then produced 
by material which streams from the egg. Broek- 
huysen (1936: 281) has raised many objections 
to this idea, concluding that it is a physical 
impossibility. 
LIFE HISTORY, STAGES, AND DURATION 
The life cycles of four of the most common 
xanthid crabs in the southern California area 
were worked out and compared by the writer. 
Of the four published life cycles of British 
Columbia Brachyura by Hart (1935: 414), one 
is of a xanthid crab, Lophopanopeus bellus bellus 
(Stimpson). The data given by Hart compare 
favorably with those obtained by the writer, thus 
permitting a discussion which may be applicable 
to the entire family. 
The eggs are attached to the pleopods and 
there incubated from 25 to 30 days. The female 
periodically flexes and extends her abdomen as 
if to allow fresh sea water to wash and aerate 
the eggs. From time to time the female plucks 
eggs or other material from the egg mass with 
her chelae, and conveys this to her mouth. The 
exact reason for such action is not known, but it 
may be a method of cleaning the eggs. In the 
field it was noted that ovigerous females of 
Lophopanopeus b. diegensis, Lophopanopeus l. 
leucomanus, and Paraxanthias taylori were often 
stranded by minus, low tides. These animals 
make no attempt to enter tidepools a few inches 
below them, but rather remain in their hiding 
places. The abdomen of such animals is closed 
over the egg mass, thus keeping considerable 
water around the eggs. In the laboratory a tall 
rock-filled water jar was stocked with ovigerous 
xanthid females. The sea water was then slowly 
siphoned out in an attempt to simulate the 
lowering of tides. Paraxanthias taylori and Loph- 
opanopeus l. leucomanus did not follow the 
receding water, but stayed out of water where 
they finally died. Eggs kept out of water in moist 
algae up to 6 hours were viable when returned 
to water. Thus periodic withdrawal of water 
under normal tidal conditions has no apparent 
effect on the eggs. 
Hatching occurred most frequently at night 
shortly after dark. Occasionally a few individ- 
uals of a given egg mass will hatch during the 
daylight hours, but these are followed by mass 
emergence of the other larvae at night. Hatch- 
ing begins as the egg capsule splits about half- 
way around, above the dorsal surface of the 
larva. The larva struggles out of the capsule, 
dorsal side up, and swims free of the mother 
crab. During the peak of the hatching period 
the flexion and extension of the females ab- 
domen increases very noticeably. With each 
flexion many larvae are washed away from the 
egg mass. 
The prezoea (the larva just after hatching) 
has its maxillipeds, antennules, antennae, telson, 
and spines telescoped. There is no apparent 
ecdysis between this stage and the first zoea. 
Rather, the folded extremities are extended by 
haemocoelic fluid as is the case after normal 
ecdysis. Hiatt (1948: 204), however, reports 
true ecdysis after the prezoeal stage in Pachy- 
grapsus crassipes. Healthy prezoeae swim for 30 
minutes to 2 hours before the expansion is com- 
plete. When the larvae are completely expanded 
they are called zoeae. 
There are typically four zoeal stages and one 
megalops stage in the xanthid life history. The 
zoeae are pelagic, photopositive forms which 
