Animalia Life

Carapus bermudensis
FAMILY
Carapidae
TAXONOMY
Lefroyia bermundensis Jones, 1874, Bermuda. The holotype was named in honor of Lefroy, a former governor of Bermuda. The species is now valid as Carapus bermudensis (Jones) following several taxonomic revisions. Numerous names are probably referable to C. bermudensis, including C. recifensis, C. chavesi, and Fierasfer dubius. C. bermudensis may be related most closely to C. acus, its eastern Atlantic relative. The species-level relationships of the genus, however, are poorly known.
OTHER COMMON NAMES
None known.
PHYSICAL CHARACTERISTICS
Carapus bermudensis is long, slender, and eel-like, with a large head and relatively large eyes. It is translucent, with silvery bands along the flanks, black internal pigment visible along the vertebral column, a silver cheek patch, and large pigment blotches along the bases of the dorsal and anal fins and head. The anal fin origin is anterior to the dorsal fin origin. There are 13–18 anal rays anterior to the first dorsal ray. This number varies among pearlfish species and is useful in identification. There are no pelvic fins, and the caudal fin usually is absent. The pectoral fin has 17–20 rays. The teeth on the upper jaw are small, and some are heart-shaped. The teeth on the lower jaw are larger and conical. The air bladder is separated into two parts by an internal constriction under vertebrae 11 and 12. This feature of the internal anatomy is characteristic of all species in the genus Carapus, and the position of the constriction relative to the vertebrae allows for separation of species.
DISTRIBUTION
Distributed in shallow waters along the shores of the western Atlantic, Bermuda, and the Caribbean Sea south to Brazil. Its larvae sometimes are collected far north and east of this range in plankton samples taken by research cruises.
HABITAT
All species of the genus Carapus have obligatory commensal relationships with sea cucumbers (Holothuria), starfishes (Asterioidea), or sea squirts (Ascidiacea). Many species exhibit host specificity. Carapus bermudensis has been collected in the body cavity of nine holothurian species in the genera Actinopyga, Isostichopus, Thone, Astichopus, Holothuria, and Theelothuria. These host species generally reside in shallow waters, to about 98.4 ft (30 m) on sandy bottoms or grass beds in tropical and subtropical lagoons near reefs. In one study in the Bahamas, pearlfishes were found in relatively few restricted areas, although more than 1,000 sea cucumbers were surveyed.
BEHAVIOR
Resides within the body of its host during daylight and is believed to exit at night to forage and perhaps spawn. This strategy limits the probability of predation by larger fishes. This species has been observed in aquaria as it rapidly enters its primary host, Actinopyga agassizi. The species first locates the anal opening of the sea cucumber with its snout, presumably through olfaction. As the fish holds its head in the proper position at the anal opening, the body curves and the tip of the tail tracks along the mid-lateral line until it reaches the anus. Once the tail tip is aligned and pointed into the opening, the fish abruptly turns, forcing its way tail first into the host by body undulations. There are no observations of living pearlfishes in the wild and little data on its habits and
BEHAVIOR
s.
FEEDING ECOLOGY AND DIET
Some inquiline pearlfishes are parasitic, dining on the internal organs of the invertebrates they occupy. This species of pearlfish is not parasitic and feeds outside the holothurian host, probably at night. There have been no detailed studies of the food habits of this species, but gut contents of individuals are mostly crustacean invertebrates, such as amphipods, small shrimps, crabs, and mysids. Rarely, a pearlfish is found in the stomach of larger, predaceous fishes.
REPRODUCTIVE BIOLOGY
Spawning of pearlfishes has not been observed, and carapid reproductive
BEHAVIOR
is poorly known. Some investigators have identified eggs collected in plankton samples by subsequent incubation in the laboratory. There also are a few reports of pearlfish species spawning in aquaria. In these cases, the scientists did not observe spawning directly but found eggs in tanks after periods of darkness. The eggs of pearlfishes are ellipsoid, usually containing an oil droplet and deposited into a jellylike, mucous matrix that floats at the surface. The egg mass has been described as oval, spherical, or somewhat flattened. Eggs hatch in one to two days. Early larvae are easily identified, since they possess a vexillum that first appears as a small protuberance but rapidly grows in length. Older pearlfish larvae have a long pigmented and ornamented vexillum that often is damaged in collection. Pearlfish larvae are extremely elongate, reaching about 7.1 in (180 mm) in length, and possess a distinct small ring of melanophores on the snout. Larvae are remarkable, in that they undergo two separate growth phases: the first as vexillifer larvae that become very elongate and the second as tenuis larvae that shrink to about half their original length.
CONSERVATION STATUS
Not listed by the IUCN.
SIGNIFICANCE TO HUMANS
This species is rarely observed and is not fished commercially.

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