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Some Pearlfishes from Guam, with Notes on Their Ecology

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Title:Some Pearlfishes from Guam, with Notes on Their Ecology
Authors:Smith, C.L.
Date Issued:Jan 1964
Publisher:University of Hawai'i Press
Citation:Smith CL. 1964. Some pearlfishes from Guam, with notes on their ecology. Pac Sci 18(1): 34-40.
Abstract:From October, 1960, 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 nouaguineae. Carapus mourlani was found only
in Culcita; the other three occurred in two or more hosts. Thelenota
ananas, Stichopus chloronotus, and an unidentified Holothuria contained
only one species each, but Holothuria 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
Holothuria atra were opened without finding a single pearlfish. Although
this species has been reported as a host, it is probably not a
preferred one.
The most common species is Carapus homei, its usual host is Stichopus
chloronotus. Tenuis larvae were collected from October through February.
Repeated collections in the same area of Tumon Bay indicated that
there was a decrease in the infestation rate after February. C. homei
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. homei 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 homei also eats
shrimp. Encheliophis gracilis, however, seems to feed on the gonads of
its host. C. homei 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 homei 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.
Appears in Collections: Pacific Science Volume 18, Number 1, 1964

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