Some Pearlfishes from Guam, with Notes on Their Ecology 
C. Lavett Smith 1 
ABSTRACT: From October, I960, to July, 1961, 230 specimens of 
pearlfishes were collected on the fringing reefs of Guam. Four forms 
are represented and their distinguishing features are discussed. These 
specimens were taken from four species of holothurians and from the 
armless starfish, Culcita novaguineae. Carapus mourlani was found only 
in Culcita; the other three occurred in two or more hosts. Thelenota 
ananas, Stick opus chloronotus, and an unidentified Holotburia contained 
only one species each, but Holotburia argus served as host of three 
pearlfish species. Sea cucumbers that produce adhesive threads as well 
as those that do not were utilized as hosts. Over 100 specimens of 
Holotburia atra were opened without finding a single pearlfish. Al- 
though this species has been reported as a host, it is probably not a 
preferred one. 
The most common species is Carapus bomei, its usual host is Sticbopus 
chloronotus . Tenuis larvae were collected from October through Febru- 
ary. Repeated collections in the same area of Tumon Bay indicated that 
there was a decrease in the infestation rate after February. C. bomei 
probably spawns in late summer, and the larvae assume the inquiline 
habit during the fall and winter months. Small samples from other 
parts of the island indicate that infestation rates vary with the locality. 
It is unusual to find more than one pearlfish in a single host, and the 
fish .are not confined to the respiratory trees but are often found free 
in the body cavity. During the period when the tenuis larvae are present 
C. bomei often feeds on the larvae of its own species, perhaps indicating 
that there is competition for hosts. This could account for the infrequent 
occurrence of more than one fish per host. Carapus bomei also eats 
shrimp. Encheliophis gracilis, however, seems to feed on the gonads of 
its host. C. bomei leaves the host at night and on four occasions was 
seen some distance from any probable hosts. 
The form called Carapus mourlani is structurally very similar to C. 
bomei but differs in having superficial melanophores. Since mourlani 
occurs only in Culcita and bomei never does, there is a possibility that 
the observed differences are due to the effects of the host. Until this 
can be demonstrated experimentally it seems desirable to retain the 
name mourlani. 
IT is well KNOWN that some pearlfishes (fam- 
ily Carapidae) dwell within the bodies of 
echinoderms and other invertebrates, although 
1 Department of Zoology, University of Hawaii, 
Honolulu. 
Present address : The American Museum of Natural 
History, New York. 
Manuscript received June 15, 1962. 
few of the recognized species have been studied 
in detail. Arnold (1956) revised the family and 
thoroughly surveyed the literature but some no- 
menclatural problems remain, owing to the un- 
availability of the types of certain nominal 
forms. Schultz (1960:393) has emphasized the 
need for studies of series of specimens from 
various hosts ". . . in order to furnish sufficient 
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