Zoeal Stages and Glaucothoe of Trizopagurus magni ficus — Provenzano 
459 
hatched has been deposited in the U. S. Na- 
tional Museum (Catalog No. 113559). 
EXPERIMENTAL RESULTS 
Effect of Starvation at Various Temperatures 
In order to determine the maximum survival 
time for unfed animals, several trays of larvae 
without food were placed in each experimental 
temperature. At 25°, 20°, and 15°C, 7-8 days 
were required for 50% mortality of the 54 
starved larvae in each temperature, but at 10°C 
only 3 days were required for 50% mortality 
of 36 larvae. At 25 °C, total mortality of the 
starved group required 10-12 days; at 20 °C, 
9-11 days; at 15°C, 8-10 days; and at 10°C 
all larvae were dead by the sixth day after 
hatching. 
Survival at Various Temperatures of Larvae 
Fed with Artemia 
At 10°C, 36 larvae were placed two per 
compartment. They began dying on the third 
day and by the seventh day all were dead. At 
15°C, 145 larvae were placed one, two, or five 
per compartment. None moulted to stage II. 
By 21 days after hatching, approximately one- 
half had died, but a few survived as long as 
35 days, then died in stage I. 
At 20°C, 329 larvae were placed in trays, 
one, two, four, or more per compartment. 
Most moulted to stage II within 13-18 days 
after hatching, but a few lived to stage III. 
None became glaucothoe, but three specimens 
lived to stage V and died at approximately 85 
days after hatching. 
At 25 °C, 305 larvae were placed in trays, 
one, two, or four per compartment. Nearly all 
survived the first moult, which took place 7-8 
days after hatching. Glaucothoes were obtained 
at this temperature in as few as 33 and as many 
as 52 days after hatching. Only 18 glaucothoes 
were obtained. One specimen spent 23 days as 
a glaucothoe, then died in the moult to first 
crab stage, 56 days after hatching. 
CAUSES OF MORTALITY 
At 10°C the mortality of fed animals paral- 
leled quite closely that for starved animals, in- 
dicating either that, despite presence of food, 
the animals were unable to feed or that the 
temperature alone was sufficiently low to kill 
the animals directly. Even at the higher tem- 
peratures starved larvae did not swim during 
the last few days. Hence we may suppose that 
in nature larvae unable to feed within the 
first few days after hatching seldom survive 
as long as they did in these experiments, but 
nothing is known of the capacity of larvae to 
resume feeding and normal growth after vary- 
ing periods of starvation. The shorter survival 
time at lower temperatures indicates that, at 
least at temperatures below 25 °C, the exhaus- 
tion of yolk reserves was not the factor causing 
death among starved larvae, but that tempera- 
ture had a direct negative effect on survival. 
Because of the large number of larvae hatched 
and the limited time available to tend to them, 
some were placed together in compartments. 
It is unlikely that crowding was a primary 
cause of mortality since each compartment con- 
tained 40-60 ml of water and, in a few 
compartments in which as many as 10 larvae 
were together, survival was better than in many 
others with fewer animals. There was no ap- 
parent negative effect of crowding on survival. 
It is obvious that the temperatures used 
were mostly below the satisfactory range for 
this species. At 10°C the larvae could not swim 
and died very quickly even though they had 
been gradually reduced to that temperature 
from the hatching temperature of only about 
18°C. At 15°C the larvae were below the 
temperature at which normal development must 
take place, since none of them were able to 
moult. The fact that some lived as long as 35 
days indicates that a few must have been able 
to feed at least occasionally even at that tem- 
perature, for starved larvae at 15°C were all 
dead by the tenth day after hatching. Even at 
20 °C larvae were apparently under very mar- 
ginal conditions, since only three out of 329 
lived to stage V. 
At 25 °C, although the percentage of sur- 
vival to metamorphosis was low (18 glau- 
cothoes were obtained from 305 original lar- 
vae), and although none of the glaucothoes 
actually survived to crab stage, the temperature 
was probably satisfactory, if still less than 
optimal. Contributing to the high mortality 
under laboratory conditions at 20° and 25°C 
