38 
PACIFIC SCIENCE, Vol. XVIII, January 1964 
Fig. 1. Heads of four species of pearlfishes from Guam, a, Encheliophis gracilis, total length 182 mm. 
b, Carapus mourlani, 91 mm. c, Carapus homei, 113 mm. d, Carapus parvipinnis, 238 mm. 
finding as many as five Carapus ( bermudensis ) 
in a single holothurian host in the Bahamas, 
but I have never seen more than two in an 
individual host. Moreover, the total number of 
inquilines never exceeded the total number of 
hosts in any one collection. It is possible, then, 
that some of the few "twins” observed may have 
been postcapture transfers. 
SEASONAL VARIATIONS 
of the hosts because all areas have approximately 
the same density of hosts except Asan. The Asan 
area is peculiar in that there is a very strong 
flow of water over the edge of the reef and a 
dense population of Stick opus chloronotus. 
Aronson and Mosher (1951:489) also reported 
different levels of pearlfish infestation in dif- 
ferent parts of the Bimini harbour. 
ACTIVITY OUTSIDE OF THE HOST 
Repeated collections in Turnon Bay indicate 
that there is a decrease in rate of infestation 
from November to June (Table 3). It is sug- 
gested that this is not due to sampling error 
alone, because only the collections made from 
November to February contained tenuis larvae. 
This would seem to indicate that the tenuis 
enter the host during the late fall and winter 
months and at that time there is a high rate of 
infestation. As the season progresses there is 
loss through mortality and the incidence de- 
creases. It would be of interest to follow this 
through several complete cycles to obtain data 
on recruitment and mortality rates. 
There are also different rates of infestation 
in different areas of the reefs (Table 4). This 
variation is not correlated with the abundance 
It has been suggested that some pearlfishes 
never leave the host unless it eviscerates, but 
this is certainly not true of Carapus homei or 
Encheliophis gracilis. C. homei seems to leave 
the host regularly during the night and on four 
occasions I observed free swimming individuals 
between 9 and 11 P.M. One of these was taken 
in a commercial fisherman’s beach seine; the 
others were seen hovering about 18 inches 
above the bottom in water 3 or 4 ft deep. The 
fish, observed as I swam along with an under- 
water flashlight and a face mask, remained mo- 
tionless until I came within a foot or two of 
them. I was able to catch one in a hand net; 
the others escaped. In neither of the latter cases 
was there a Stick opus host nearby and my efforts 
to chase one into a host were unsuccessful. 
