Carapus bermudensis

Geographic Range

Atlantic pearlfish are native to tropical western Atlantic waters from Bermuda to Brazil, including southern Florida, the Gulf of Mexico and the West Indies. Larvae of this species have also been found in the Gulf of Maine.

• Biogeographic Regions
• nearctic nearctic
  • native native
• neotropical neotropical
  • native native
• atlantic ocean atlantic ocean
  • native native

Habitat

Atlantic pearlfish are tropical and subtropical marine benthic teleosts. They are primarily commensal, commonly being found living inside the bodies of sea cucumbers (Holothuroidea) or occasionally other marine intervebrates. These fish tend to be associated with coral-dominated communities or shallow sea grass beds, and are most common at depths of 1-34 meters, although they have been found in waters up to 235 meters deep.

• Habitat Regions
• tropical tropical
• saltwater or marine saltwater or marine

• Aquatic Biomes
• benthic benthic
• reef reef
• coastal coastal

Physical Description

This species is characterized by a short predorsal region and a dorsal fin which is longer than the anal fin, extending along the body and meeting at the ends of the tail. The anus is located anteriorly, close to the throat. The body is scaleless and eel-like in appearance, being long and laterally compressed. There are no enlarged dentary or premaxillary fangs, spaces between their teeth. Pectoral and pelvic fins are also absent. These fish have constricted, two-chambered swim bladders, as well as visceral cradles and elaborate pre-dorsal bones. They have small conical teeth all along their jaws, as well as cardiform teeth on the frontal, external regions of the premaxillary bones. Coloration is typically silver and white, with red markings. Adults range in length from 15 to 24 cm total length, though individuals found at extreme depths have been noted to be both larger and darker in color. Vexillifer larvae (the first stage of metamorphosis) of this species are relatively deep bodied, with a short predorsal body region.

• Other Physical Features
• ectothermic ectothermic
• bilateral symmetry bilateral symmetry

• Sexual Dimorphism
• sexes alike

Development

Although its complete life history and development have yet to be described, it is assumed that eggs of this species follow a similar pattern to a closely related species, Carapus actus . Eggs are laid in a gelatinous flat that floats freely in open waters. After hatching from elliptical, planktonic eggs, larvae undergo two separate growth phases. In the first phase, the larvae develop into vexillifers, which are characterized by a branched dorsal filament called the vexillum. As the vexillifers continue to grow, they lose their vexilla and enter the tenuis stage. Atlantic pearlfish larvae in this stage are very long (7-8 cm) and thin, transparent, and develop a long caudal filament. At this stage, these fish become demersal and may enter a host or remain free-swimming. Once they have entered a host (tail first, through its anus), they transform into their definitive forms, shrinking to about one third of their tenuis length, beginning to grow again after transformation is complete. This larval period is estimated to last for three months.

• Development - Life Cycle
• metamorphosis metamorphosis

Reproduction

Little is known of the reproductive behavior of Atlantic pearlfish. While many carapids pair sexually, this speices is thought to be an open-water broadcast spawner, with females scattering eggs over substrate and males releasing sperm over them.

• Mating System
• polygynandrous (promiscuous) polygynandrous (promiscuous)

Atlantic pearlfish are dioecious and breed via broadcast spawning throughout the year; larvae in both vexillifer and tenuis stages, as well as adults, can be found at any time of year. Following external fertilization, eggs hatch within one or two days. It is unknown how many eggs are released at a time or what age these fish are when they reach sexual maturity, as time to adulthood has not been recorded.

• Key Reproductive Features
• iteroparous iteroparous
• year-round breeding year-round breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual sexual
• fertilization fertilization
  • external external
• broadcast (group) spawning
• oviparous oviparous

As broadcast spawners, adults of this species show no parental investment.

• Parental Investment
• no parental involvement

Lifespan/Longevity

Using otolith data, the average lifespan of this species in the wild has been estimated to be 3 years.

Behavior

Atlantic pearlfish are both commensal and parasitic endosymbionts of holothurians. the preferred host for this species appears to be Actinopyga agassizi , though they are found in body cavities of other holothurian species as well. These fish search for hosts by swimming with their heads towards the bottom, searching for water currents exhaled from a potential host. Entrance is typically through a host's anus, after which a fish may remain in the gut or bite through to the alimentary canal or respiratory tree. Atlantic pearlfish typically enter their hosts tail-first, though they are known to enter head first as well. Unlike other families in this order, carapids are not known to be parasitic, using their hosts for shelter only. Although uncommon, it is possible for more than one fish to live in one host. Atlantic pearlfish leave their hosts at dusk to feed, and re-enter hosts by daylight.

• Key Behaviors
• natatorial natatorial
• nocturnal nocturnal
• motile motile
• sedentary sedentary
• solitary solitary

Home Range

These fish do not have a well defined home range; they may return to the same host each night after feeding, but it is not necessary.

Communication and Perception

Atlantic pearlfish are able to produce sounds, which are structured in regular pulse emissions and are heard over long distances from within their hosts. These sounds signal their sex to conspecifics. In sexual encounters, sounds are reduced to a single pulse emission. Sound emissions can be divided into two groups: stridulatory (non-harmonic sounds created by rubbing body parts against each other, such as teeth and pectoral fins) and swim bladder vibrations (sounds from vibration of the swim bladder against a deformation of its wall). These vibrations are detected by other Atlantic pearlfish through their lateral line systems. These fish locate potential hosts primarily using chemical cues as well as through vision, olfaction and rheotaxis (sensation of water currents).

• Communication Channels
• visual visual
• tactile tactile
• acoustic acoustic
• chemical chemical

• Other Communication Modes
• vibrations vibrations

• Perception Channels
• visual visual
• tactile tactile
• acoustic acoustic
• vibrations vibrations
• chemical chemical

Food Habits

Atlantic pearlfish are nocturnal carnivores, capturing the vast majority of prey while outside of their hosts; Caridean shrimps are their main source of food and they also occasionally feed on other small decapods, isopods, annelids, copepods, and fish remains. They are nonspecific generalists, eating whatever food is most abundant and easily attainable. They may cannibalize smaller conspecifics.

• Primary Diet
• carnivore carnivore
  • eats non-insect arthropods

• Animal Foods
• fish
• carrion carrion
• mollusks
• aquatic or marine worms
• aquatic crustaceans
• other marine invertebrates
• zooplankton zooplankton

Predation

These fish are well protected from predation by their hosts, sometimes even feeding while still halfway inside their hosts. They are able to take advantage of their hosts' anti-predator adaptations, such as their Cuverian tubules; these are not activated when an Atlantic pearlfish enters and these fish also have a higher tolerance to sea cucumber toxins than other reef fish do. Potential predators include other fishes, including conspecifics and other ophidiiform species.

Ecosystem Roles

Atlantic Pearlfish affect their benthic marine ecosystems by regulating populations of their prey, including small crustaceans. They have a well-known commensal relationship with sea cucumbers, using their hosts for protection. This does not generally adversely affect individual sea cucumbers or their populations.

Economic Importance for Humans: Positive

This species does not have any economic value or other benefit to humans.

Economic Importance for Humans: Negative

There are no known adverse effects of this species on humans.

Conservation Status

Atlantic Pearlfish are not listed or have not yet been evaluated by any specific conservation initiative. Individuals are technically "protected" when their sea cucumber hosts live within a protected reef zone, such as the Florida Keys National Marine Sanctuary.

Additional Links

Encyclopedia of Life

Contributors

Stephanie Chong (author), San Diego Mesa College, Derek Sheldon (author), San Diego Mesa College, Paul Detwiler (editor), San Diego Mesa College, Jeremy Wright (editor), University of Michigan-Ann Arbor.

References

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IUCN, 2012. "The IUCN Red List of Threatened Species" (On-line). Accessed February 18, 2013 at http://www.iucnredlist.org/search .

Johnson, C., J. Runge, K. Curtis, E. Durbin, J. Hare, L. Incze, J. Link, G. Melvin, T. O'Brien, L. Van Guelpen. 2011. Biodiversity and ecosystem function in the Gulf of Maine: pattern and role of zooplankton and pelagic nekton. PLOS One , 6/1: e16491. Accessed February 16, 2013 at http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0016491#pone.0016491.s002 .

Jones, K. 1874. "FISHWISE Species Detail Page" (On-line). Fisahwise. Accessed September 24, 2012 at http://www.fishwise.co.za/Default.aspx?TabID=110&GenusSpecies=Carapus_bermudensis&SpecieConfigId=201538 .

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Parmentier, E., P. Vandewalle. 2003. Morphological adaptations of pearlfish (Carapidae) to their various habitats. Pp. 261-276 in Fish Adaptations . India: Oxford& IBH.

Robins, R., R. Carleton, J. Douglas, R. Freund. 1986. A Field Guide to Atlantic Coast Fishes of North America . Boston: Houghton Mifflin Company.

Smith, C., J. Tyler, M. Feinberg. 1981. Population ecology and biology of the pearlfish ( Carapus bermudensis ) in the lagoon at Bimini, Bahamas. Bulletin of Marine Science , 31(4): 876–902. Accessed September 27, 2012 at http://absci.fiu.edu/wp-content/uploads/2012/03/Pearlfish.pdf .

Smith, C., J. Tyler. 1969. Observations on the Commensal Relationship of the Western Atlantic Pearlfish, Carapus bermudensis, and Holothurians. Copeia , 1: 206-208. Accessed February 18, 2013 at http://www.jstor.org/discover/10.2307/1441726?uid=3739832&uid=2129&uid=2134&uid=4577548977&uid=2&uid=70&uid=3&uid=4577548967&uid=3739256&uid=60&purchase-type=both&accessType=none&sid=21101693451251&showMyJstorPss=false&seq=3&showAccess=false .

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National Ocean Service. 2013. "Florida Keys National Marine Sanctuary Regulations" (On-line). Accessed February 18, 2013 at http://floridakeys.noaa.gov/regs/welcome.html .