Cusk-eel

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The cusk-eel family, Ophidiidae, is a group of marine bony fishes in the Ophidiiformes order. The scientific name is from the Greek ophis meaning "snake", and refers to their eel-like appearance. True eels, however, diverged from other ray-finned fish during the Jurassic, while cusk-eels are part of the Percomorpha clade, along with tuna, perch, seahorses, and others.

Distribution

Cusk-eels are found in temperate and tropical oceans throughout the world. They live close to the sea bottom, ranging from shallow water to the hadal zone. One species, Abyssobrotula galatheae, was recorded at the bottom of the Puerto Rico trench, making it the deepest recorded fish at 8,370 m (27,460 ft).[1][2]

Ecology

Cusk-eels are generally very solitary in nature, but some species have been seen to associate themselves with tube worm communities.[3] Liking to be hidden when they are not foraging, they generally associate themselves within muddy bottoms, sinkholes, or larger structures that they can hide in or around, such as caves, coral crevices, or communities of bottom-dwelling invertebrates, with some parasitic species of cusk-eel actually living inside of invertebrate hosts, such as oysters, clams, and sea cucumbers.[3] Cusk-eels generally feed nocturnally, preying on invertebrates, crustaceans, and other small bottom-dwelling fishes.

Phylogeny

Due to the inconsistencies in specific morphological characteristics in closely related species, attempts to use different characters, such as the position of pelvic fins, to classify Ophiididae into distinct families has proven highly unsatisfactory. Overall, Ophidiidae are classified based on whether or not they practice viviparity and the structures they contain that are associated with bearing life.[3]

Characteristics

Cusk-eels are characterized by a long, slender body that is about 12-13 times as long as it is deep. The largest species, Lamprogrammus shcherbachevi, grows up to 2 m (6.6 ft) in length, but most species are shorter than 1 m (3.3 ft). Their dorsal and anal fins are typically continuous with the caudal fin (with exception to a few species), forming a long, ribbon like fin around the posterior of the cusk-eel’s body.[4] This caudal fin will often be seen to be reduced to a fleshy or bony point, especially when confluent with the dorsal and anal fins. The dorsal fin to anal fin ray ratio is approximately 1.5:1, leading to the dorsal fin typically being longer than the anal. The pectoral fins of cusk-eels are typically longer than the length of their head. Unlike true eels of the order Anguilliformes, cusk-eels have ventral fins that are developed into a forked barbel-like organ below the mouth. In true eels by contrast, the ventral fins are never well-developed and usually missing entirely.[5] Cusk-eels have large mouths relative to their heads, with the upper jaw reaching beyond the eye, and paired nostrils on either side of the head. In cusk-eels, scales are potentially absent, and when present, they are small.[4]

Reproduction

Unlike their close relatives, the viviparous brotulas of the family Bythitidae, cusk-eel species are egg-bearing, or oviparous, organisms. While the specifics of the eggs of the family Ophidiidae are unknown, they are believed to be either spawned as individual, free-floating eggs in the open water or are placed in a mucilaginous raft, which will float for several days until they hatch into cusk-eel larvae. These larvae live amongst the plankton relatively close to the water's surface[1] and are believed to be able to control their metamorphosis into adult cusk-eels, allowing them to disperse over greater distances into less utilized habitats and reduce competition in concentrated areas.[3]

Conservation status

While a few species are fished commercially – most notably the pink cusk-eel, Genypterus blacodes – and several species of the order Ophidiiformes are listed as vulnerable, not enough information has been gathered about Ophidiidae as a whole to determine their conservation status.

Genera

The cusk-eel family contains about 240 species, grouped into 50 genera:[6]
Subfamily Brotulinae

Subfamily Brotulotaenilinae

Subfamily Neobythitinae

Subfamily Ophidiinae

Gallery

References

  1. ^ a b Nielsen, Jørgen G. (1998). Paxton, J.R.; Eschmeyer, W.N. (eds.). Encyclopedia of Fishes. San Diego: Academic Press. p. 134. ISBN 0-12-547665-5.
  2. ^ "What is the deepest-living fish?". Australian Museum. 23 December 2014. Retrieved 18 September 2015.
  3. ^ a b c d "Ophidiiformes (Cusk-Eels and Relatives) | Encyclopedia.com". www.encyclopedia.com. Retrieved 2021-04-27.
  4. ^ a b Bigelow, Andrew (2002). Bigelow and Schroeder's fishes of the Gulf of Maine. Washington, DC: Smithsonian Institution Press.
  5. ^ Froese, Rainer, and Daniel Pauly, eds. (2006). "Ophidiidae" in FishBase. February 2006 version.
  6. ^ Froese, Rainer, and Daniel Pauly, eds. (2008). "Ophidiidae" in FishBase. December 2008 version.

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Cusk-eel: Brief Summary

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The cusk-eel family, Ophidiidae, is a group of marine bony fishes in the Ophidiiformes order. The scientific name is from the Greek ophis meaning "snake", and refers to their eel-like appearance. True eels, however, diverged from other ray-finned fish during the Jurassic, while cusk-eels are part of the Percomorpha clade, along with tuna, perch, seahorses, and others.

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Pearlfish

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Pearlfish are marine fish in the ray-finned fish family Carapidae. Pearlfishes inhabit the tropical waters of the Atlantic, Indian, and Pacific Oceans at depths to 2,000 m (6,600 ft), along oceanic shelves and slopes. They are slender, elongated fish with no scales, translucent bodies, and dorsal fin rays which are shorter than their anal fin rays. Adults of most species live symbiotically inside various invertebrate hosts, and some live parasitically inside sea cucumbers. The larvae are free living.

Characteristics

Pearlfishes are slender, distinguished by having dorsal fin rays that are shorter than their anal fin rays. They have translucent, scaleless bodies reminiscent of eels. The largest pearlfish are about 50 cm (20 in) in length. They reproduce by laying oval-shaped eggs, about 1 mm in length.[2]

Ecology

Pearlfishes are unusual in that the adults of most species live inside various types of invertebrates. They typically live inside clams, starfish, or sea squirts, and are simply commensal, not harming their hosts. However, some species are known to be parasitic on sea cucumbers, eating their gonads and living in their anal pores. Pearlfish usually live alone, or in pairs.[3]

Regardless of the habits of the adults, the larvae of pearlfish are free-living among the plankton. Pearlfish larvae can be distinguished by the presence of a long filament in front of their dorsal fins, sometimes with various appendages attached.[2]

Genera

The genera are divided into three major groupings based on their level of symbiosis:

References

  1. ^ Richard van der Laan; William N. Eschmeyer & Ronald Fricke (2014). "Family-group names of Recent fishes". Zootaxa. 3882 (2): 001–230.
  2. ^ a b Nielsen, Jørgen G. (1998). Paxton, J.R.; Eschmeyer, W.N. (eds.). Encyclopedia of Fishes. San Diego: Academic Press. p. 133. ISBN 0-12-547665-5.
  3. ^ The fish that lives in a sea cucumber anus, Australian Geographic, 8 August 2014
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Pearlfish: Brief Summary

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Pearlfish are marine fish in the ray-finned fish family Carapidae. Pearlfishes inhabit the tropical waters of the Atlantic, Indian, and Pacific Oceans at depths to 2,000 m (6,600 ft), along oceanic shelves and slopes. They are slender, elongated fish with no scales, translucent bodies, and dorsal fin rays which are shorter than their anal fin rays. Adults of most species live symbiotically inside various invertebrate hosts, and some live parasitically inside sea cucumbers. The larvae are free living.

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Description

provided by World Register of Marine Species
Chiefly marine (rarely freshwater). Distribution: Atlantic, Indian, and Pacific Oceans. Anus and anal fin origin usually posterior to pectoral fin tip. Anal fin rays usually of the same length or shorter than opposing dorsal fin rays. Scales present. One or more opercular spines in some. Supramaxillary present. Vexillum lacking in larvae. Pelvics usually present. About 1.5 m maximum length.
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MASDEA (1997).
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Distribution

provided by World Register of Marine Species
Distribution: tropical and subtropical Atlantic, Indian, and Pacific Oceans. Dorsal fin rays shorter than opposite anal rays. Anus of adults and origin of anal fin located behind head and usually under pectoral fin. No scales. Wide gill openings, reaching far forward. Vomerine, palatine and jaw teeth present. No opercular spines. Branchiostegal rays 6-7. No supramaxillary. Vertebrae about 85-145. Vexillum present in larvae. Pearlfishes are free-living (Echiodon), commensal (Carapus, Onuxodon), or parasitic (Encheliophis, Jordanicus), living in association with shallow-water invertebrate hosts (holothurians, bivalves, starfishes), largely in coral-dominated communities. Family members occur in shelf and slope waters of 0-2,000 m depth and range from about 65°N to 60°S.
license
cc-by-4.0
copyright
WoRMS Editorial Board
bibliographic citation
MASDEA (1997).
contributor
Edward Vanden Berghe [email]