86 
PACIFIC SCIENCE, VoL XXI, January 1967 
RESPONSES TO AMBIENT WATER TEMPERATURE 
Reactions to Cold Temperature 
P. carmelensis placed in sea water at a tem- 
perature of 3°C immediately contracted into a 
U-shaped posture with normally ventral portion 
of the animal forming the inside surface of the 
U. Few animals exposed to this temperature 
had noticeable muscular or ciliary motion while 
in this posture. Thus, the well-developed auto- 
maticity normally associated with ciliary motion 
(Prosser and Brown, 1961) apparently did not 
occur in P. carmelensis exposed to sea water 
at 3°C After several minutes’ exposure, disinte- 
gration of the epidermal cells occurred, and 
shortly thereafter a gentle motion of the water 
caused by stirring with a probe resulted in dis- 
organization of the body structure. 
All polychoerus exposed to an ambient water 
temperature of 5°C contracted into the U- 
shaped posture and were motionless for several 
minutes. Thereafter most were capable of loco- 
motion (it was necessary to test 24 individuals 
to obtain locomotion rates for 20 animals). 
These animals were motile long enough to mea- 
sure locomotion rates ranging from 5.0 to 32.5 
mm/min with an average of 17.4 mm/min. 
This was the lowest average obtained in these 
tests. At the same temperature, 16 individuals 
moved about while in the U-shaped posture. 
Apparently this movement was accomplished 
entirely by motion of cilia on the dorsal surface, 
since no muscular contractions were noticed as 
the animals glided over the surface of the plas- 
tic grid. These animals moved about for only 
a minute or two and thereafter tissue disintegra- 
tion took place as described above. The highest 
rates of locomotion at 5°C were obtained from 
4 animals that, after a short period in the U- 
shaped posture, moved in the typical flatworm 
posture. Within a few minutes movement 
ceased, whereupon they again contracted into 
the U-shaped posture and died. 
Reactions to Changes in Ambient Water 
Temperature 
The locomotion rate of P. carmelensis was 
clearly influenced by the temperature of am- 
bient sea water under the conditions of these 
experiments. However, there were pronounced 
changes in the manner in which locomotion 
occurred. Several of the 20 animals exposed to 
water at 8°C began to move while in the U- 
shaped posture. Locomotion was accomplished 
by action of the dorsal cilia, the only portion i 
of the body in contact with the plastic grid. 
These animals soon reoriented to the typical 
flatworm posture and the rate of locomotion at 
8°C was measured from this posture only. At 
this temperature Polychoerus traveled at an av- 
erage rate of 44.9 mm/min. Accelerated loco- 
motion rates associated with increases in am- [ 
bient water temperatures were measured at 11°, 
14°, and 17°C with average values of 64.8, 
83.0, and 90.4 mm/min respectively. Thus, the 
average rate of locomotion for P. carmelensis 
acclimated at 13°-l4°C increased from 17.4 to 
90.4 mm/min in response to a 12 -degree rise i 
(from 5° to 17°C) in temperature. This in- 
crease in speed of locomotion took place at a 
nearly uniform rate of 6.1 mm/min/°C in- 
crease in water temperature (see Table 1). 
P. carmelensis specimens respond to tempera- 
tures higher than 17°C by decreasing their rate 
of locomotion. A reduction in average loco- 
motion rate was measured at 21°C (78.5 
mm/min), 25°C (66.2 mm/min), 29°C (50.2 
mm/min), and 33°C (32.8 mm/min). This 
results in a steady decrease in the speed of 
locomotion at an approximate rate of 4.4 ! 
mm/min/ °C rise in temperature between 17° 
and 33°C. 
Reactions to Warm T emperatures 
At an ambient water temperature of 29° C 
Polychoerus usually contracted into a curled I 
position with the posterior portion of the body 
drawn up under the more anterior portion. Lo- 
comotion in this posture was primarily accom- 
plished by action of the anterior portion of the 
body, since much of the posterior portion was 
not in contact with the plastic grid. The animals 
had an average locomotion rate of 50.2 mm/min 
while in this posture and, although several ani- 
mals died after 5-10 minutes’ exposure, it is 
reasonable to assume that they would have 
found a more suitable temperature within this 
length of time in their natural habitat. 
Most of the individuals exposed to an am- 
bient water temperature of 33 °C immediately 
contracted into the curled posture, mentioned 
above and were capable of locomotion for only 
