User:MicroMarine/sandboxproject

Source: Wikipedia, the free encyclopedia.
This page 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: Early Carboniferous–Present
Hydrolagus colliei
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Chondrichthyes
Subclass: Holocephali
Order: Chimaeriformes
Obruchev, 1953
Families

Chimaeras

rattails, Opisthoproctidae, or Siganidae
, respectively.

At one time a "diverse and abundant" group (based on the

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
electroreceptor
cells.

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.[4]

Like other members of the class

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
. Chimeras move throughout the water with a combination of body undulations and pectoral fin flapping. They use these fins to "fly" through water.

Chimaeras resemble sharks in some ways: they employ

electroreception to find their prey.[5] However, unlike sharks, male chimaeras also have retractable sexual appendages on the forehead (a type of tentaculum)[6] and in front of the pelvic fins.[4] 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

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.[4] Furthermore, they have true nostrils (along with gills). These nostrils are found under the snout, just above the mouth. Water can be drawn in through these nostrils and then pass over the gills[7]
.

Distribution

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

public aquaria. They live in all the oceans except for the Arctic and Antarctic oceans. Chimeras have a high degree of endemism with about 37% of species only found in one area of the world[8]. One third of the species documented are found in the Southwest Pacific. Younger chimaeras typically occupy deeper waters than their adult counterparts[8]
.

Currently, there are three extant families; Callorhinchidae, Rhinochimaeridae and Chimaeridae. The distribution of each family varies greatly, and may not completely capture all areas that inhabit due to the lack of research [Image showing the distribution of the three extant families would be included here][9].

Growth and reproduction

Unlike 75% of the class of Chondrichthyes that give birth to live young (ovoviviparity and viviparity), Chimaera’s lay their young in eggs (Oviparous), often referred to as Mermaids Purses, which is a leathery case that will hatch in 6-12 months. Additionally, when females lay their eggs, they are paired and remained attached to the female for a period of time before attaching to the seabed[10]. The process of egg-laying takes around 18-30 hours and can occur every 10-14 days throughout the breeding season (which is 6-8 months long), indicating an annual fecundity range of 19.5 - 28.9[8]. Chimaera’s exhibit sexual dimorphism, where males reach sexual maturity after reaching a length of 18.5 - 20 cm, and females reach sexual maturity when they reach a length of 24 - 25 cm[10]. 

The eggs of the chimera can reach up to 10 cm long. After incubation, the eggs will hatch and young chimera will appear at about roughly 14 cm in length. The chimaera does not have a larval stage as they are fully developed once they hatch[8]. Unlike other sharks, it is hard to age ghost sharks. They lack the hard internal structures which are typically used to age other chondrichthyans. Estimates from various studies and observations place chimaeras with a maximum age estimate of about 40 years[11][12].

Diet

As mentioned in the description and habits section, chimaera, unlike sharks have three pairs of large permanent grinding tooth plates[13]. In addition to this, Chimaeras are not strong swimmer, which further limits their diet to bottom dwelling invertebrates such as crabs, clams, shrimp, and small benthic fish. In addition to small invertebrates, they have been known to eat their own egg cases and even other chimaeras[10].

Phylogenetics

Tracing the evolution of these species has been problematic given the paucity of good fossils. DNA sequencing has become the preferred approach to understanding speciation.[14]

The group containing Chimeras and their close relatives (

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.[17] 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

Chimaera monstrosa
; the species can attain 50 mm (2.0 in) in length.

Threats and Concerns

Climate Change

Climate change can have an effect on chimeras. Because they are deep-sea organisms, there is moderate exposure to climate change factors. This includes rising temperature as this affects their physicochemical environment.[18] The rising sea temperatures could lead to a change in the distribution of the chimaeras. This change in distribution is not yet known [8]. These changes could also affect currents and upwelling which will lead to a negative impact on the productivity in the deep ocean.[18]

By-catch

In addition to climate change, another major threat to chimaeras is overfishing by the means of by-catch, through deep-sea and inshore trawling activities. These activities can threaten the stability of the species population because they're a deep-sea fish which often means they grow at a slower rate and reach reproductive maturity later in life[19].

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.

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

See also

References

  1. ^ a b Froese, Rainer, and Daniel Pauly, eds. (2014). "Chimaeriformes" in FishBase. November 2014 version.
  2. ^ 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. ISBN 0-618-00212-X
    . Retrieved 9 August 2015.
  4. ^
    ISBN 0-12-547665-5
    .
  5. ISBN 978-3-642-65926-3
    .
  6. ^ 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. ...
  7. ^ Devocean, Shark (2014-08-26). "Introducing: Chimaeras". Shark Devocean. Retrieved 2022-04-09.
  8. ^
    ISSN 1467-2960. {{cite journal}}: Check date values in: |date= (help
    )
  9. ^ "IUCN Red List".
  10. ^ a b c Pacific, Aquarium of the. "Spotted Ratfish". www.aquariumofpacific.org. Retrieved 2022-04-09.
  11. ISSN 0250-6408
    .
  12. ISSN 0045-8511. {{cite journal}}: Check date values in: |date= (help
    )
  13. ISSN 0175-8659. {{cite journal}}: Check date values in: |date= (help
    )
  14. PMID 20551041
    . Retrieved 14 November 2018.
  15. ^
    S2CID 239509836
    .
  16. S2CID 128402250
    .
  17. S2CID 198423356
    .
  18. ^
    doi:10.1111/j.1365-2486.2009.02128.x
    .
  19. ISSN 0137-1592
    .
  20. S2CID 229433827
    .
  21. ^ Iglésias, S.P., Kemper, J.M. & Naylor, G.J.P. Chimaera compacta, a new species from southern Indian Ocean, and an estimate of phylogenetic relationships within the genus Chimaera (Chondrichthyes: Chimaeridae). Ichthyol Res 69, 31–45 (2022). https://doi.org/10.1007/s10228-021-00810-9
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