Chimaera

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This article is about the cartilaginous fish order. For the namesake genus, see Chimaera (genus). For the mythological beast, see Chimera (mythology). For other uses, see Chimera.
"Ghost shark" redirects here. For the film, see Ghost Shark (film).

Chimaeras
Temporal range: Late Triassic–Present
Hydrolagus colliei.jpg
Hydrolagus colliei
Scientific classification e
Kingdom: Animalia
Phylum: Chordata
Class: Chondrichthyes
Subclass: Holocephali
Order: Chimaeriformes
, 1953
Families

Chimaeras[1] are cartilaginous fish in the order Chimaeriformes /kɪˈmɛrɪfɔːrmiːz/, known informally as ghost sharks, rat fish, spookfish, or rabbit fish; the last three names are not to be confused with rattails, Opisthoproctidae, or Siganidae, respectively.

At one time a "diverse and abundant" group (based on the fossil record), their closest living relatives are sharks and rays, though their last common ancestor with them lived nearly 400 million years ago.[2] Today, they are largely confined to deep water.[3]

Description and habits[]

Chimaera egg case
Deep-sea chimaera photographed by the NOAAS Okeanos Explorer. Visible on its snout are tiny pores which lead to electroreceptor cells.

Chimaeras live in temperate ocean floors down to 2,600 m (8,500 ft) deep, with few occurring at depths shallower than 200 m (660 ft). Exceptions include the members of the genus Callorhinchus, the rabbit fish and the spotted ratfish, which locally or periodically can be found at relatively shallow depths. Consequently, these are also among the few species from the chimaera order kept in public aquaria.[4] They live in all the oceans except for the Arctic and Antarctic.

They have elongated, soft bodies, with a bulky head and a single gill-opening. They grow up to 150 cm (4.9 ft) in length, although this includes the lengthy tail found in some species. In many species, the snout is modified into an elongated sensory organ.[5]

Like other members of the class Chondrichthyes, chimaera skeletons are constructed of cartilage. Their skin is smooth and naked, lacking placoid scales (except in the claspers), and their color can range from black to brownish gray. For defense, most chimaeras have a venomous spine in front of the dorsal fin. They use these fins to "fly" through water.

Chimaeras resemble sharks in some ways: they employ claspers for internal fertilization of females and they lay eggs with leathery cases. They also use electroreception to find their prey.[6] However, unlike sharks, male chimaeras also have retractable sexual appendages on the forehead (a type of tentaculum)[7] and in front of the pelvic fins.[5] The females lay eggs in spindle-shaped, leathery egg cases.[1]

They also differ from sharks in that their upper jaws are fused with their skulls and they have separate anal and urogenital openings. They lack sharks' many sharp and replaceable teeth, having instead just three pairs of large permanent grinding tooth plates. They also have gill covers or opercula like bony fishes.[5]

Phylogenetics[]

Tracing the evolution of these species has been problematic given the scarcity of good fossils. DNA sequences have become the preferred approach to understanding speciation.[8]

The group containing Chimeras and their close relatives (Holocephali) is thought to have originated about 420 million years ago during the Silurian. The earliest known remains attributable to modern chimaeras first appear in the Early Jurassic (Pleinsbachian) of Europe, but egg cases from the Late Triassic of Yakutia, Russia and New Zealand[9] that resemble those of rhinochimaerids and callorhinchids respectively indicates that they had a global distribution prior to the end of the Triassic. Unlike modern chimaeras, Mesozoic representatives are often found in shallow water settings.[10] The extant species fall into three families—the Callorhinchidae, Rhinochimaeridae and Chimaeridae with the callorhinchids being the most basal clade.

Parasites[]

As other fish, chimaeras have a number of parasites. Chimaericola leptogaster (Chimaericolidae) is a monogenean parasite of the gills of Chimaera monstrosa; the species can attain 50 mm (2.0 in) in length.

Classification[]

In some classifications, the chimaeras are included (as subclass Holocephali) in the class Chondrichthyes of cartilaginous fishes; in other systems, this distinction may be raised to the level of class. Chimaeras also have some characteristics of bony fishes.

A renewed effort to explore deep water and to undertake taxonomic analysis of specimens in museum collections led to a boom during the first decade of the 21st century in the number of new species identified.[2] A preliminary study found 8% of species to be threatened.[11] There are 50 extant species in six genera and four families are described; an additional three genera and two families are only known from fossils):

Callorhinchus callorynchus
Chimaera monstrosa
Hydrolagus affinis
Harriotta raleighana
  • †Suborder Myriacanthoidei Patterson 1965 (Late Triassic-Late Jurassic)
    • †Family
      • † Zittel 1887 Belgium, Early Jurassic (Sinemurian)
    • †Family Myriacanthidae Woodward 1889
      • †Acanthorhina Fraas 1910 Posidonia Shale Formation, Germany, Early Jurassic (Toarcian)
      • †Agkistracanthus Duffin and Furrer 1981 Austria, England and Switzerland, Late Triassic-Early Jurassic (Rhaetian-Sinemurian)
      • †Alethodontus Duffin 1983 Germany, Early Jurassic (Sinemurian)
      • † Duffin 1984 Belgium and Luxembourg, Early Jurassic (Sinemurian)
      • †Metopacanthus Zittel 1887 Posidonia Shale Formation, Germany, Early Jurassic (Toarcian)
      • † Duffin and Milàn 2017 Hasle Formation, Denmark, Early Jurassic (Pliensbachian)
      • † Agassiz 1837 United Kingdom, Late Triassic-Early Jurassic (Rhaetian-Sinemurian)
      • † Duffin 1981 United Kingdom, Early Jurassic (Sinemurian)
  • Suborder Chimaeroidei Patterson 1965
    • † Ward and Duffin 1989 United Kingdom, Early Jurassic (Pleinsbachian)
    • Family Callorhinchidae Garman, 1901
    • Family Chimaeridae Bonaparte, 1831
      • Genus Chimaera Linnaeus, 1758
        • Chimaera argiloba Last, & Pogonoski, 2008 (whitefin chimaera)
        • Chimaera bahamaensis , , & Compagno, 2010 (Bahamas ghost shark)
        • Chimaera cubana Howell-Rivero, 1936
        • Chimaera fulva , Last & , 2008 (southern chimaera)
        • Chimaera jordani S. Tanaka (I), 1905 (Jordan's chimaera)
        • Chimaera lignaria , 2002 (carpenter's chimaera)
        • Chimaera macrospina , Last & , 2008 (longspine chimaera)
        • Chimaera monstrosa Linnaeus, 1758 (rabbit fish)
        • Chimaera notafricana , , Compagno & , 2010 Cape chimaera
        • Chimaera obscura , Last & , 2008 (shortspine chimaera)
        • Chimaera opalescens , & , 2011
        • Chimaera owstoni S. Tanaka (I), 1905 (Owston's chimaera)
        • Chimaera panthera , 1998 (leopard chimaera)
        • Chimaera phantasma Jordan & Snyder, 1900 (silver chimaera)
      • Genus Hydrolagus Gill, 1863
        • Hydrolagus affinis , 1868 (smalleyed rabbitfish)
        • Hydrolagus africanus Gilchrist, 1922 (African chimaera)
        • Hydrolagus alberti Bigelow & Schroeder, 1951
        • Hydrolagus alphus , , & , 2006 (whitespot ghost shark)
        • Hydrolagus barbouri Garman, 1908
        • Hydrolagus bemisi , 2002 (pale ghost shark)
        • Hydrolagus colliei Lay & E. T. Bennett, 1839 (spotted ratfish)
        • Hydrolagus deani H. M. Smith & Radcliffe, 1912 (Philippine chimaera)
        • Jordan & Hubbs, 1925
        • Hydrolagus homonycteris , 2008 (black ghostshark)
        • Hydrolagus lemures Whitley, 1939 (blackfin ghostshark)
        • , , , & , 2005
        • Hydrolagus macrophthalmus de Buen, 1959
        • Hydrolagus marmoratus , 2008 marbled ghostshark
        • Hydrolagus matallanasi & , 2004 (striped rabbitfish)
        • Hydrolagus mccoskeri , , & , 2006 (Galápagos ghostshark)
        • Hydrolagus melanophasma , , & , 2009 (Eastern Pacific black ghostshark)
        • Hydrolagus mirabilis Collett, 1904 (large-eyed rabbitfish)
        • Hydrolagus mitsukurii Jordan & Snyder, 1904 (spookfish)
        • Hydrolagus novaezealandiae Fowler, 1911 (dark ghostshark)
        • Hydrolagus ogilbyi Waite, 1898
        • Hydrolagus pallidus & , 1990
        • Hydrolagus purpurescens Gilbert, 1905 (purple chimaera)
        • Hydrolagus trolli & , 2002 (pointy-nosed blue chimaera)
        • Fowler, 1907
    • Family Rhinochimaeridae Garman, 1901
      • Genus Harriotta Goode & Bean, 1895
        • Harriotta haeckeli , 1972 (smallspine spookfish)
        • Harriotta raleighana Goode & Bean, 1895 (Pacific longnose chimaera)
      • Genus Neoharriotta Bigelow & Schroeder, 1950
        • Neoharriotta carri & , 1966 (dwarf sicklefin chimaera)
        • Neoharriotta pinnata Schnakenbeck, 1931 (sicklefin chimaera)
        • Neoharriotta pumila & , 1996 (Arabian sicklefin chimaera)
      • Genus Rhinochimaera Garman, 1901
        • Rhinochimaera africana Compagno, & , 1990 (paddle-nose chimaera)
        • Rhinochimaera atlantica Holt & Byrne, 1909 (straightnose rabbitfish)
        • Rhinochimaera pacifica Mitsukuri, 1895 (Pacific spookfish)

See also[]

References[]

  1. ^ Jump up to: a b Froese, Rainer, and Daniel Pauly, eds. (2014). "Chimaeriformes" in FishBase. November 2014 version.
  2. ^ Jump up to: a b "Ancient And Bizarre Fish Discovered: New Species Of Ghostshark From California And Baja California". ScienceDaily. September 23, 2009. Retrieved 2009-09-23.
  3. ^ Peterson, Roger Tory; Eschmeyer, William N.; Herald, Earl S. (1 September 1999). A Field Guide to Pacific Coast Fishes: North America. Houghton Mifflin Harcourt. p. 13. ISBN 0-618-00212-X. Retrieved 9 August 2015.
  4. ^ Tozer, Helen; Dagit, Dominique D. (2004). "Chapter 33: Husbandry of Spotted Ratfish, Hydrolagus colliei" (PDF). In Smith, Mark; Warmolts, Doug; Thoney, Dennis; Heuter, Robert (eds.). Elasmobranch Husbandry Manual: Captive Care of Sharks, Rays, and their Relatives. Ohio Biological Survey. pp. 487–491. ISBN 0-86727-152-3.[permanent dead link]
  5. ^ Jump up to: a b c Stevens, John; Last, Peter R. (1998). Paxton, John R.; Eschmeyer, William N. (eds.). Encyclopedia of Fishes. San Diego: Academic Press. p. 69. ISBN 0-12-547665-5.
  6. ^ Bullock, T. H.; Hartline, R. H.; Kalmijn, A. J.; Laurent, P.; Murray, R. W.; Scheich, H.; Schwartz, E.; Szabo, T. (6 December 2012). Fessard, A. (ed.). Electroreceptors and Other Specialized Receptors in Lower Vertebrates. Springer Science & Business Media. p. 125. ISBN 978-3-642-65926-3.
  7. ^ Madrigal, Alexis (22 September 2009). "Freaky New Ghostshark ID'd Off California Coast". Wired. Retrieved 14 November 2018. ... Perhaps the most intriguing feature of the newly described species, Hydrolagus melanophasma, is a presumed sexual organ that extends from its forehead called a tentaculum. ...
  8. ^ Inoue, Jun G.; Miya, Masaki; Lam, Kevin; Tay, Boon-Hui; Danks, Janine A.; Bell, Justin; Walker, Terrence I.; Venkatesh, Byrappa (November 2010). "Evolutionary Origin and Phylogeny of the Modern Holocephalans (Chondrichthyes: Chimaeriformes): A Mitogenomic Perspective". Molecular Biology and Evolution. 27 (11): 2576–2586. doi:10.1093/molbev/msq147. PMID 20551041. Retrieved 14 November 2018.
  9. ^ Gottfried, Michael D.; Fordyce, R. Ewan (2015-05-04). "A Late Triassic chimaeroid egg capsule from New Zealand: early evidence of chimaeroid reproductive mode from the eastern margin of Gondwana". Journal of Systematic Palaeontology. 13 (5): 371–375. doi:10.1080/14772019.2014.880752. ISSN 1477-2019. S2CID 128402250.
  10. ^ Popov, Evgeny V.; Delsate, Dominique; Felten, Roland (2019-07-02). "A New Callorhinchid Genus (Holocephali, Chimaeroidei) from the Early Bajocian of Ottange-Rumelange, on the Luxembourg-French Border". Paleontological Research. 23 (3): 220. doi:10.2517/2018PR021. ISSN 1342-8144.
  11. ^ Finucci, Brittany; Cheok, Jessica; Ebert, David A.; Herman, Katelyn; Kyne, Peter M.; Dulvy, Nicholas K. (2021). "Ghosts of the deep – Biodiversity, fisheries, and extinction risk of ghost sharks". Fish and Fisheries. 22 (2): 391–412. doi:10.1111/faf.12526. ISSN 1467-2979.
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