Brachyura and Anomura of Puget Sound — KNUDSEN 
11 
ulation is completed, the female generally 
scrambles off backwards while the male at- 
tempts to right himself. 
Hiatt (1948:199) suggests that Pachygrap- 
sus eras sipes copulates mainly at night, as his 
total observations were few in relation to the 
amount of observation time. In our work, how- 
ever, we have noted that H. nudus was seen 
most often in copulation during the day under 
lighted conditions (12 records) rather than at 
night ( 2 records ) . Our observation time during 
the breeding season was, by far, greater in the 
daytime and thus we have no firm conclusion 
as to the preferred time, or light condition, for 
copulation. Probably this species will copulate 
at any time that the female is receptive and 
there is no outside disturbance. 
FERTILIZATION AND EGG DEPOSITION: Bi- 
monthly counts of up to several hundred fe- 
males allowed us to trace the onset of egg 
deposition through two entire seasons. The date 
at which egg deposition began and the rate of 
deposition .during the second year was remark- 
ably close to that of the first year for both 
species, and differed only by about 5 days in 
either direction. Thus, on or shortly before New 
Year’s Day, egg deposition begins and continues 
extremely rapidly. Ricketts and Calvin (1952: 
31) note that this species produces eggs as early 
as November in Monterey Bay, California, in 
contrast to Puget Sound specimens. Perhaps 
water temperature may have some influence, 
although in both areas temperatures are declin- 
ing at the time of deposition. Fertilization oc- 
curs as the eggs are discharged through the 
vulvae, at which time they are attached to the 
pleopods. A remarkable 98.66% of all females 
examined were found to have eggs early in 
April. Nonovigerous specimens examined at 
this time showed no development within the 
ovary and probably were unhealthy or beyond 
a reproductive age. Figure 1 shows that hatch- 
ing begins rapidly early in May and reaches a 
peak toward the end of that month. By the first 
weeks in June all of the eggs have hatched. At 
this time less than 1% of all of the females 
examined showed the production of a second 
brood or a new brood. 
productivity: Fifty-one females of all size 
classes of H. nudus were selected for egg counts. 
The sizes ranged from 11.9 mm in carapace 
width up to 34.0 mm in carapace width, and 
the number of eggs varied from 441 up to 
36,456 eggs for the two extremes of sizes. The 
average number for all 51 specimens was 13,000 
per brood. Since only one brood is produced per 
year this figure probably can be used as the 
average annual production for this species. 
LARVAL DEVELOPMENT: H. nudus has been 
studied and completely described in its larval 
development by Hart (1935:424-430). There 
are five zoea stages and one megalops stage. 
Hemigrapsus oregonensis 
FOOD AND FEEDING HABITS: Throughout the 
year 12 specimens were preserved for stomach 
content studies. Of the 12, 2 had totally empty 
stomachs and 2 had only partially full stom- 
achs. Like H. nudus, members of this species 
had been feeding upon diatoms and other algal 
forms obtained by scraping the upper surfaces of 
rocks within the intertidal zone. The diatoms 
were the same sessile forms as described for 
H. nudus. However, most of the individuals 
had some green algae, probably Ulva and Enter - 
omorpha, but none had any fragments of ani- 
mal tissue within the stomach. H. oregonensis 
lives somewhat lower in the intertidal zone than 
does H. nudus, and at this level a large quantity 
of Ulva is found attached to the rocks. Thus, it 
seems quite natural that this green alga should 
be used as a source of food. In the laboratory 
H. oregonensis will consume animal tissue such 
as fish or cut clam or even fragments of crab 
muscle tissue, and thus must be considered a 
scavenger when dead animal tissue is available. 
This species is predominantly a herbivore, how- 
ever, and is considered to obtain most of its 
food from plant sources. Hemigrapsus oregonen- 
sis feeds in the same manner as H. nudus, but 
is more timid in its behavior. 
Both. H. oregonensis and H. nudus use the 
tactile, visual, and chemical senses in their feed- 
ing. While gleaning from the rocks at night the 
tactile senses are presumably used almost ex- 
clusively, for the eyes would be of little value 
in this situation. Chemoreceptors on the tips of 
the walking legs could possibly be used to de- 
termine the presence of marine algae. In the 
experimental aquarium these species can locate 
bits of meat by means of chemoreceptors and 
