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chimaera

 
Dictionary: Chi·mæ·ra
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n.

[NL. See Chimera.]
(Zoöl.) A cartilaginous fish of several species, belonging to the order Holocephali. The teeth are few and large. The head is furnished with appendages, and the tail terminates in a point.

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Britannica Concise Encyclopedia: chimera
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Any of the 28 species of ancient fishes constituting the subclass Holocephali (class Chondrichthyes), found in temperate to cold waters of all oceans. Like sharks and rays, chimeras have a skeleton of cartilage rather than bone, and the males possess external reproductive organs (claspers). They have a single external gill opening, covered by a flap as in the bony fishes, on each side of the body. Males have a supplemental clasping organ that is unique among fishes. Chimeras have large pectoral and pelvic fins and two dorsal fins, the first preceded by a sharp spine. They range in length from 24 to 80 in. (60 to 200 cm) and in colour from silvery to blackish. They inhabit rivers, estuaries, coastal waters, and open ocean to depths of 8,000 ft (2,500 m) or more. They eat small fishes and invertebrates.

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Columbia Encyclopedia: chimaera
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chimaera (kĭmēr'ə), cartilaginous marine fish, related to the sharks. Also called ratfishes, chimaeras are found in temperate oceans throughout the world, mostly in deep water. They have large heads, long, thin, ratlike tails, and large, fanlike pectoral fins. In many species there is a poison spine in front of the first dorsal fin. Their slippery skins are black, gray, or silver, often with stripes or spots. The largest reach a length of about 61/2 ft (2 m). Chimaeras resemble sharks in certain fundamental respects: They have cartilage skeletons, males have claspers for internal fertilization of females, and females lay eggs encased in leathery cases. However, they resemble the bony fishes in having the upper jaw fused to the skull, the gill slits opening into a single chamber, a bony covering, or operculum, over the gill slits, and separate anal and urogenital openings. A distinctive feature of chimaeras is the presence of extra claspers in the male, one in front of each pelvic fin and a prominent one on the forehead. The function of these appendages is not known, but they are thought to play a role in courtship. Chimaeras form the subclass Holocephali of the phylum Chordata, subphylum Vertebrata, class Chondrichthyes.

WordNet: chimaera
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Note: click on a word meaning below to see its connections and related words.

The noun has 2 meanings:

Meaning #1: a grotesque product of the imagination
  Synonym: chimera

Meaning #2: smooth-skinned deep-sea fish with a tapering body and long threadlike tail

Wikipedia: Chimaera
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This article is about the cartilaginous fish order. For the namesake genus, see Chimaera (genus). For other uses, see Chimera (disambiguation).
Chimaeras
Fossil range: Early Devonian-Recent[1]
Hydrolagus colliei
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Chondrichthyes
Subclass: Holocephali
Order: Chimaeriformes
Families

Callorhinchidae
Chimaeridae
Rhinochimaeridae

Chimaeras are cartilaginous fish in the order Chimaeriformes, known informally as ghost sharks, ratfish (not to be confused with the rattails), or rabbitfishes (not to be confused with the "true" rabbitfishes of the family Siganidae). They may be the "oldest and most enigmatic groups of fishes alive today."[2] At one time a "diverse and abundant" group (based on the fossil record), their closest living relatives are sharks, though in evolutionary terms they branched off from sharks nearly 400 million years ago and have remained isolated ever since, typically confined to deep water.[2]

Contents

Description and habits

Chimaeras live in temperate ocean floors down to 2,600 metres (8,500 ft) depth, and most do not occur at depths shallower than 200 metres (660 ft). Exception include the members of the genus Callorhinchus, the rabbit fish and the spotted ratfish, which locally/periodically can be found at relatively shallow depths. Consequently, these are also among the only species from the Chimaera order that are kept in public aquaria.[3] They have elongated, soft bodies, with a bulky head and a single gill-opening. They grow up to 150 centimetres (4.9 ft) in length, although this includes the – in some species – lengthy tail. In many species, the snout is modified into an elongated sensory organ.[4]

Like other members of the class Chondrichthyes, chimaeras have a skeleton constructed of cartilage. Their skin is smooth and lacks scales, and their color can range from black to brownish gray. For defense, most chimaeras have a venomous spine located in front of the dorsal fin.

Chimaeras resemble sharks in some ways: they employ claspers for internal fertilization of females and they lay eggs with leathery cases. However, unlike sharks, male chimaeras also have retractable sexual appendages on the forehead (a type of tentaculum)[5] and in front of the pelvic fins.[4] The females lay eggs in spindle-shaped leathery 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 the many sharp and replaceable teeth of sharks, having instead just three pairs of large permanent grinding tooth plates.[4]

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 have led to a boom during the first decade of the 21st century in the number of new species identified.[2] There are about forty extant species in six genera and three families (an additional three genera and two family are only known from fossils):

Elephantfish, Callorhinchus callorynchus

Family Callorhinchidae

Chimaera monstrosa

Family Chimaeridae

Smalleyed rabbitfish, Hydrolagus affinis

Family Rhinochimaeridae

Family †Squalorajidae

Family †Echinochimaeridae

See also

References

Specific references:

  1. ^ a b "Chimaeriformes". FishBase. Ed. Ranier Froese and Daniel Pauly. January 2009 version. N.p.: FishBase, 2009.
  2. ^ a b c "Ancient And Bizarre Fish Discovered: New Species Of Ghostshark From California And Baja California". ScienceDaily. September 23, 2009. http://www.sciencedaily.com/releases/2009/09/090922095816.htm. Retrieved 2009-09-23. 
  3. ^ Tozer, H., & D. D. Dagit (2004). Husbandry of Spotted Ratfish, Hydrolagus colliei.
  4. ^ a b c Stevens, J. & Last, P.R. (1998). Paxton, J.R. & Eschmeyer, W.N.. ed. Encyclopedia of Fishes. San Diego: Academic Press. p. 69. ISBN 0-12-547665-5. 
  5. ^ Freaky New Ghostshark ID’d Off California Coast, a September 22, 2009 blog post from Wired Science
  6. ^ Quaranta et al. (2006). "A new species of chimaeroid, Hydrolagus alphus sp. nov. (Chimaeriformes: Chimaeridae) from the Galapagos Islands". Zootaxa 1377: 33–45. http://www.mapress.com/zootaxa/2006f/z01377p045f.pdf. 

General references:

v • d • e
Extant chondrichthyes orders by superorder
Kingdom Animalia · Phylum Chordata · Subphylum Vertebrata · Infraphylum Gnathostomata
Batoidea
Selachimorpha
Holocephali
Chimaeriformes

This entry is from Wikipedia, the leading user-contributed encyclopedia. It may not have been reviewed by professional editors (see full disclaimer)

 
 

 

Copyrights:

Dictionary. Webster 1913 Dictionary edited by Patrick J. Cassidy  Read more
Britannica Concise Encyclopedia. Britannica Concise Encyclopedia. © 2006 Encyclopædia Britannica, Inc. All rights reserved.  Read more
Columbia Encyclopedia. The Columbia Electronic Encyclopedia, Sixth Edition Copyright © 2003, Columbia University Press. Licensed from Columbia University Press. All rights reserved. www.cc.columbia.edu/cu/cup/.  Read more
WordNet. WordNet 1.7.1 Copyright © 2001 by Princeton University. All rights reserved.  Read more
Wikipedia. This article is licensed under the Creative Commons Attribution/Share-Alike License. It uses material from the Wikipedia article "Chimaera".  Read more