Pearlfishes from Guam- — S mith 
37 
TABLE 2 
Host Specificity in Some Guam Pearlfishes 
INQUILINE 
N 
HOST SPECIES 
Stichopus 
chloronotus 
Thelenota 
ananas 
Hoi. 
argus 
Hoi 
species 
Culcita 
novaguineae 
Encheliophis gracilis 
15 
1 
— 
12 
2 
— 
Carapus parvipinnis 
2 
— 
1 
1 
— 
— 
Carapus homei 
208 
187 
— 
21 
— 
— 
Carapus mourlani 
5 
— 
— 
— 
— 
5 
None 
— 
196 
0 
17 
17 
9 
Total 
230 
384 
1 
51 
19 
14 
dorsal surface) harbored only Encheliophis gra- 
cilis. Thelenota ananas (Jaeger) contained only 
Carapus parvipinnis , although in the latter case 
only one specimen was examined. Both of these 
hosts have habits that may impose limits on the 
species of inquilines inhabiting them; Thelenota 
lives in deeper water off the edge of the reef 
and the Holothuria burrows in sandy areas of 
the moat. 
Holothuria atra has been reported as a pearl- 
fish host but it seems to be, at best, a second 
choice. In Tumon Bay, Guam, I examined 107 
atra without finding any pearlfishes, although 
more than 80% of the Stichopus chloronotus 
from the same part of the bay contained Carapus 
homei. There is some difference in the habitats 
of these two holothurians; atra is most abundant 
in quiet, shallow, sandy parts of the moat, 
whereas Stichopus lives on harder bottom near 
the edge of the reef where there is a good flow 
of fresh sea water. The ranges of the two over- 
lap, however, and I have observed C. homei at 
night in places where atra was more common 
than Stichopus. The suggestion that H. atra is 
not a preferred host is supported by Bonham’s 
statement (1960:255) that no pearlfishes were 
found in several hundred atra from the Marshall 
Islands, although there was a Carapus homei in 
the single Stichopus he examined. Strasburg 
(1961:479) also reported a low incidence of 
Encheliophis gracilis in H. atra from Hawaii 
(one pearlfish in 114 atra examined). 
The ability of some holothurians to produce 
adhesive threads when molested might be pos- 
tulated as a factor in their suitability as a pearl- 
fish host. Holothuria argus and Holothuria sp. 
are thread producers; Thelenota ananas and 
Stichopus chloronotus are not. Thus, it appears 
that Carapus homei and C. parvipinnis are found 
in both types but Encheliophis gracilis shows a 
preference for thread producers. Holothuria atra, 
occasionally reported as the host of Encheliophis 
gracilis (Strasburg, 1961:479; Schultz, I960: 
393) and E. vermicularis (Schultz, 1960:393), 
is not a thread producer but the incidence of 
pearlfishes in that species is low. 
When the host is cut open the violent move- 
ments of the fish make it difficult to determine 
the original location of the fish within the host. 
Most individuals seemed to be free in the body 
cavity but a few were in the respiratory trees 
and some of these became so wedged in that the 
section with the fish could be removed and pre- 
served in formalin without the fish freeing itself. 
Bonham (1960:255) carefully floated the host 
into a plastic bag and froze it before opening 
so as to avoid any disturbance. With these pre- 
cautions he found the fish free in the body 
cavity. Some species of pearlfishes appear to 
feed on the viscera of the holothurian and there- 
fore must leave the respiratory trees. Carapus 
mourlani is found free in the coelom of its 
starfish host which, of course, has no respiratory 
trees. Thus, it appears that these species, at least, 
are not confined to the respiratory tubes but 
are able to insinuate themselves into the body 
cavity. 
Aronson and Mosher (1951:489) reported 
