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Carapus bermudensisAtlantic pearlfish

By Stephanie Chong and Derek Sheldon

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. ("Carapus bermudensis: Pearlfish", 2012; Froese and Kesner-Reyes, 2012; Johnson, et al., 2011)

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. (Froese and Kesner-Reyes, 2012; Parmentier and Vandewalle, 2003; Trott, 1981; Tyler, et al., 1992)

  • Range depth
    1 to 235 m
    3.28 to 771.00 ft

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. (Froese and Kesner-Reyes, 2012; Jones, 1874; Parmentier and Vandewalle, 2003; Robins, et al., 1986; Trott, 1981; Tyler, et al., 1992)

  • Sexual Dimorphism
  • sexes alike
  • Range length
    15 to 24 cm
    5.91 to 9.45 in

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. (Smith, et al., 1981; Trott, 1981)

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. (Froese and Kesner-Reyes, 2012; Trott, 1981; Van Meter and Ache, 1974)

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. (Froese and Kesner-Reyes, 2012; Robins, et al., 1986)

  • Breeding interval
    Atlantic pearlfish breed multiple times throughout the year.
  • Breeding season
    Breeding is year-round
  • Average number of offspring
    unknown
  • Range time to hatching
    1 to 2 days
  • Average time to independence
    unknown minutes
  • Average age at sexual or reproductive maturity (female)
    unknown minutes
  • Average age at sexual or reproductive maturity (male)
    unknown minutes

As broadcast spawners, adults of this species show no parental investment. (Froese and Kesner-Reyes, 2012)

  • 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. (Froese and Kesner-Reyes, 2012; Robins, et al., 1986; Smith, et al., 1981)

  • Average lifespan
    Status: wild
    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. (Parmentier and Vandewalle, 2003; Smith, et al., 1981; Trott, 1981)

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. (Smith, et al., 1981)

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). (Lagardère, et al., 2005; Parmentier and Vandewalle, 2005; Trott, 1981; Van Meter and Ache, 1974)

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. (Smith, et al., 1981)

  • Primary Diet
  • carnivore
    • eats non-insect arthropods
  • Animal Foods
  • fish
  • carrion
  • mollusks
  • aquatic or marine worms
  • aquatic crustaceans
  • other marine invertebrates
  • 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. (Parmentier and Vandewalle, 2005; Smith, et al., 1981)

  • Known Predators
    • Atlantic pearlfish (Carapus bermudensis)
    • Encheliophis sp. (Order Ophidiiformes, Class Actinopterygii)

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. (Smith and Tyler, 1969; Smith, et al., 1981)

Species Used as Host

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. (IUCN, 2012; "Florida Keys National Marine Sanctuary Regulations", 2013)

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.

Glossary

Atlantic Ocean

the body of water between Africa, Europe, the southern ocean (above 60 degrees south latitude), and the western hemisphere. It is the second largest ocean in the world after the Pacific Ocean.

World Map

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

Neotropical

living in the southern part of the New World. In other words, Central and South America.

World Map

acoustic

uses sound to communicate

benthic

Referring to an animal that lives on or near the bottom of a body of water. Also an aquatic biome consisting of the ocean bottom below the pelagic and coastal zones. Bottom habitats in the very deepest oceans (below 9000 m) are sometimes referred to as the abyssal zone. see also oceanic vent.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

carnivore

an animal that mainly eats meat

carrion

flesh of dead animals.

chemical

uses smells or other chemicals to communicate

coastal

the nearshore aquatic habitats near a coast, or shoreline.

ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

external fertilization

fertilization takes place outside the female's body

fertilization

union of egg and spermatozoan

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

metamorphosis

A large change in the shape or structure of an animal that happens as the animal grows. In insects, "incomplete metamorphosis" is when young animals are similar to adults and change gradually into the adult form, and "complete metamorphosis" is when there is a profound change between larval and adult forms. Butterflies have complete metamorphosis, grasshoppers have incomplete metamorphosis.

motile

having the capacity to move from one place to another.

natatorial

specialized for swimming

native range

the area in which the animal is naturally found, the region in which it is endemic.

nocturnal

active during the night

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

polygynandrous

the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.

reef

structure produced by the calcium carbonate skeletons of coral polyps (Class Anthozoa). Coral reefs are found in warm, shallow oceans with low nutrient availability. They form the basis for rich communities of other invertebrates, plants, fish, and protists. The polyps live only on the reef surface. Because they depend on symbiotic photosynthetic algae, zooxanthellae, they cannot live where light does not penetrate.

saltwater or marine

mainly lives in oceans, seas, or other bodies of salt water.

sedentary

remains in the same area

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

solitary

lives alone

tactile

uses touch to communicate

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

vibrations

movements of a hard surface that are produced by animals as signals to others

visual

uses sight to communicate

year-round breeding

breeding takes place throughout the year

zooplankton

animal constituent of plankton; mainly small crustaceans and fish larvae. (Compare to phytoplankton.)

References

2012. "Carapus bermudensis: Pearlfish" (On-line). Encyclopedia of Life. Accessed February 16, 2013 at http://eol.org/pages/205819/overview.

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

Froese, R., K. Kesner-Reyes. 2012. "Carapus bermudensis (Jones, 1874) Pearlfish" (On-line). Fishbase. Accessed February 16, 2013 at http://www.fishbase.org/summary/Carapus-bermudensis.html.

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.

Lagardère, J., S. Millot, E. Parmentier. 2005. Aspects of sound communication in the pearlfish Carapus boraborensis and Carapus homei (Carapidae). Journal of Experimental Zoology Part A: Comparative Experimental Biology, 303/12: 1066-1074. Accessed February 15, 2013 at http://www.ncbi.nlm.nih.gov/m/pubmed/16254913/.

Meyer-Rochow, V. 1979. Stomach and gut contents of Carapus mourlani from starfish and a holothurian. Annales Zoologici Fennici, 16: 287-289. Accessed February 16, 2013 at http://www.sekj.org/PDF/anzf16/anzf16-287-289.pdf.

Parmentier, E., P. Vandewalle. 2005. Further insight on carapid-holothuroid relationships. Marine Biology, 146: 455-465.

Parmentier, E., P. Vandewalle. 2003. Morphological adaptations of pearlfish (Carapidae) to their various habitats. Pp. 261-276 in A Val, B Kapoor, eds. 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. 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.

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.

Trott, L. 1981. A general review of the pearlfishes (Pisces, Carapidae). Bulletin of Marine Science, 31(3): 623–629. Accessed November 15, 2012 at http://www.ingentaconnect.com/search/article?option1=tka&value1=pearlfish&pageSize=10&index=1.

Tyler, J., R. Robins, L. Smith, G. Gilmore. 1992. Deepwater populations of the western Atlantic pearlfish Carapus bermudensis (Ophidiiformes: Carapidae). Bulletin of Marine Science, 51(2): 218–223. Accessed November 15, 2012 at http://www.ingentaconnect.com/content/umrsmas/bullmar/1992/00000051/00000002/art00007.

Van Meter, V., B. Ache. 1974. Host location by the pearlfish Carapus bermudensis. Marine Biology, 26/4: 379-383. Accessed February 16, 2013 at http://link.springer.com/article/10.1007%2FBF00391522.

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