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Batoidea

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Batoidea
Temporal range:Early Jurassic–Present[1]
Pelagic stingray,Pteroplatytrygon violacea
Scientific classificationEdit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Chondrichthyes
Subclass: Elasmobranchii
Clade: Neoselachii
Superorder: Batoidea
Compagno,1973
Orders
Synonyms
Spotted eagle ray,Aetobatus narinari

Batoideais asuperorderofcartilaginous fishes,commonly known asrays.They and their close relatives, thesharks,comprise the subclassElasmobranchii.Rays are the largest group of cartilaginous fishes, with well over 600 species in 26 families. Rays are distinguished by their flattened bodies, enlargedpectoral finsthat are fused to the head, andgill slitsthat are placed on theirventralsurfaces.

Anatomy

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See also:Batoid locomotion

Batoids are flat-bodied, and, like sharks, are cartilaginous fish, meaning they have a bonelessskeletonmade of a tough, elastic cartilage. Most batoids have fiveventralslot-like body openings calledgill slitsthat lead from thegills,but theHexatrygonidaehave six.[2]Batoid gill slits lie under thepectoral finson the underside, whereas a shark's are on the sides of the head. Most batoids have a flat, disk-like body, with the exception of theguitarfishesandsawfishes,while most sharks have a spindle-shaped body. Many species of batoid have developed their pectoral fins into broad flat wing-like appendages. Theanal finis absent. The eyes andspiraclesare located on top of the head. Batoids have a ventrally located mouth and can considerably protrude their upper jaw (palatoquadrate cartilage) away from the cranium to capture prey.[3]The jaws have euhyostylic type suspension, which relies completely on the hyomandibular cartilages for support.[4]Bottom-dwelling batoids breathe by taking water in through the spiracles, rather than through the mouth as most fish do, and passing it outward through the gills.

Reproduction

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Batoids reproduce in a number of ways. As is characteristic of elasmobranchs, batoids undergointernal fertilization.Internal fertilization is advantageous to batoids as it conserves sperm, does not expose eggs to consumption by predators, and ensures that all the energy involved in reproduction is retained and not lost to the environment.[5]Allskatesand some rays areoviparous(egg laying) while other rays areovoviviparous,meaning that they give birth to young which develop in a womb but without involvement of a placenta.[6]

The eggs of oviparous skates are laid in leathery egg cases that are commonly known asmermaid's pursesand which often wash up empty on beaches in areas where skates are common.

Capture-induced premature birth and abortion (collectively called capture-induced parturition) occurs frequently in sharks and rays when fished.[6]Capture-induced parturition is rarely considered infisheries managementdespite being shown to occur in at least 12% of live bearing sharks and rays (88 species to date).[6]

Habitat

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Most species live on the sea floor, in a variety of geographical regions – mainly in coastal waters, although some live in deep waters to at least 3,000 metres (9,800 ft). Most batoids have acosmopolitan distribution,preferring tropical and subtropical marine environments, although there are temperate and cold-water species. Only a few species, likemanta rays,live in the open sea, and only a few live in freshwater, while some batoids can live in brackish bays and estuaries.

Feeding

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Most batoids have developed heavy, rounded teeth for crushing the shells of bottom-dwelling species such assnails,clams,oysters,crustaceans,and somefish,depending on the species. Manta rays feed onplankton.

Evolution

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Batoids belong to the ancient lineage of cartilaginous fishes. Fossildenticles(tooth-like scales in the skin) resembling those of today'schondrichthyansdate at least as far back as theOrdovician,with the oldest unambiguous fossils of cartilaginous fish dating from the middleDevonian.Acladewithin this diverse family, theNeoselachii,emerged by theTriassic,with the best-understood neoselachian fossils dating from theJurassic.The oldest confirmed ray isAntiquaobatis,from thePliensbachianofGermany.[7]Thecladeis represented today bysharks,sawfish,rays andskates.[8]

Classification

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Molecular evidence refutes the hypothesis that skates and rays are derived sharks.[9]Themonophylyof theskates,thestingrays,and theelectric rayshas long been generally accepted. Along withRhinopristiformes,these comprise the four traditionally accepted major batoid lineages, as in Nelson's 2006Fishes of the World.However, the exact phylogeny of the major batoid lineages, internally and with respect to one another, has been subject to diverse treatments. The following cladogram is based on a comprehensivemorphologicalassessment of batoid phylogeny published in 2004:[10]

Chondrichthyes

However, a 2011 study significantly reevaluated the phylogeny of batoids, usingnuclearandmitochondrial DNAfrom 37taxa,representing almost all recognized families and all of the traditional four major lineages. This is a far more numerous and diverse set of sample taxa than in any previous study, producing findings reflected in the cladogram below.[1]

Chondrichthyes

Holocephali(incl.Chimaera)

Elasmobranchii

Selachimorpha(Sharks)

Batoidea

Rajiformes(Skates)

Platyrhinidae(Thornbacks)

Torpediniformes(Electric rays)

"Guitarfishes 1" (Trygonorrhinidae)

"Guitarfishes 2" (incl.Pristidae(Sawfishes))

Zanobatidae(Panrays)

Myliobatoidei(Stingrays)

This study strongly confirmed the traditionally accepted internal monophyly of skates, stingrays, and electric rays. It also recoveredpanraysassisterto the stingrays, as older morphological analyses had suggested. However, it found the Rhinopristiformes, including thesawfishesand various "guitarfishes", to beparaphyletic,comprising two distinct clades. Referred to as "Guitarfishes 1" and "Guitarfishes 2", the former contains only theTrygonorrhinidae,while the latter contains the remainder of Rhinopristiformes (the familiesGlaucostegidae,Pristidae,Rhinidae,andRhinobatidae). In addition, while traditional phylogenies often find electric rays to be the basalmost batoids, followed by the Rhinopristiformes, this analysis finds apolytomybetween skates, electric rays, andthornbacksat the base of Batoidea, with weak support for skates being the actual most basal lineage, followed by a clade uniting the electric rays and thornbacks.

TheMesozoicSclerorhynchoideaarebasalorincertae sedis;they show features of the Rajiformes but have snouts resembling those of sawfishes. However, evidence indicates they are probably the sister group to sawfishes.[11]

Order Image Common name Family Genera Species Comment
Total
Myliobatiformes Stingraysand relatives 10 29 223 1 16 33 [a][12]
Rajiformes Skatesand relatives 5 36 270 4 12 26 [b]
Torpediniformes Electric rays 4 12 69 2 9 [c][13]
Rhinopristiformes Shovelnose rays and relatives 1 2 5-7 3-5 2 [d][14]
Early Eocenefossil stingrayHeliobatis radians
Giant devil ray,Mobula mobular

OrderTorpediniformes

OrderRhinopristiformes

* the placement of these families is uncertain

OrderRajiformes

OrderMyliobatiformes

Conservation

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See also:List of threatened rays

According to a 2021 study inNature,the number of oceanic sharks and rays has declined globally by 71% over the preceding 50 years, jeopardising "the health of entire ocean ecosystems as well as food security for some of the world's poorest countries".Overfishinghas increased the global extinction risk of these species to the point where three-quarters are now threatened with extinction.[15][16][17]This is notably the case in the Mediterranean Sea - most impacted by unregulated fishing - where a recent international survey of theMediterranean Science Commissionconcluded that only 38 species of rays and skates still subsisted.[18]

Differences between sharks and rays

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All sharks and rays are cartilaginous fish,contrasting with bony fishes.Many rays are adapted for feeding on the bottom.Guitarfishesare somewhat between sharks and rays, displaying characteristics of both (though they are classified as rays).

Comparison ofElasmobranchidfish
Characteristic Sharks Guitar fish Rays
Shape laterallycompressed spindle dorsoventrallycompressed (flattened) disc
Spiracles not always present always present
Habitat usuallypelagicsurface feeders, thoughcarpet sharksaredemersalbottom feeders demersal / pelagic mix usually demersal bottom feeders
Eyes usually at the side of the head usually on top of the head
Gillopenings on the sides ventral (underneath)
Pectoral fins distinct not distinct
Tail largecaudal finwhose primary function is to provide main forward propulsion varies from thick tail as extension of body to a whip that can sting to almost no tail.
Locomotion swim by moving their tail (caudal fin) from side to side Guitar fish andsawfishhave a caudal fin like sharks swim by flapping their pectoral fins like wings

See also

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Wikimedia Commons has media related toBatoidea.

Footnotes

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  1. ^Myliobatiformesincludestingrays,butterfly rays,eagle rays,andmanta rays.They were formerly included in the orderRajiformes,but more-recentphylogeneticstudies have shown that they are amonophyletic group,and that its more-derivedmembers evolved their highly flattened shapes independently of theskates.[12]
  2. ^Rajiformesincludeskates,guitarfishes,andwedgefishes.They are distinguished by the presence of greatly enlargedpectoral fins,which reach as far forward as the sides of the head, with a generally flattened body. The undulatory pectoral fin motion diagnostic to this taxon is known as rajiform locomotion. The eyes and spiracles are located on the upper surface of the body, and the gill slits on the underside. They have flattened, crushing teeth, and are generally carnivorous. Most species give birth to live young, although some lay eggs inside a protective capsule ormermaid's purse.
  3. ^The electric rays haveelectric organsin their pectoral fin discs that generateelectric current.They are used to immobilize prey and for defense. The current is strong enough to stun humans, and theancient GreeksandRomansused these fish to treat ailments such asheadaches.[13]
  4. ^The sawfishes are shark-like in form, having tails used for swimming and smallerpectoral finsthan most batoids. The pectoral fins are attached above the gills as in all batoids, giving the fishes a broad-headed appearance. They have long, flat snouts with a row of tooth-like projections on either side. The snouts are up to 1.8 metres (6 ft) long, and 30 centimetres (1 ft) wide, and are used for slashing and impaling small fishes and to probe in the mud for embedded animals. Sawfishes can enter freshwater rivers and lakes. Some species reach a total length of 6 metres (20 ft). All species of sawfish are endangered or critically endangered.[14]

References

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  1. ^abAschliman, Neil C.; Nishida, Mutsumi; Miya, Masaki; Inoue, Jun G.; Rosana, Kerri M.; Naylor, Gavin J.P. (2012)."Body plan convergence in the evolution of skates and rays (Chondrichthyes: Batoidea)".Molecular Phylogenetics and Evolution.63(1). Elsevier BV: 28–42.doi:10.1016/j.ympev.2011.12.012.
  2. ^Martin, R. Aidan (February 2010)."Batoids: Sawfishes, Guitarfishes, Electric Rays, Skates, and Sting Rays".Elasmo research.ReefQuest Centre for Shark Research.
  3. ^Motta, P.J.; Wilga, C.D. (2001). "Advances in the study of feeding behaviors, mechanisms, and mechanics of sharks".Environmental Biology of Fishes.60(1–3): 131–56.doi:10.1023/A:1007649900712.S2CID28305317.
  4. ^Wilga, C.A.D. (2008). "Evolutionary divergence in the feeding mechanism of fishes".Acta Geologica Polonica.58:113–20.
  5. ^"Reproduction overall".Risk Section, Bedford Institute of Oceanography & Marine Fish Species.Canadian Shark Research Lab.Skates and rays of Atlantic Canada. Northwest Atlantic Fisheries Center. Archived fromthe originalon 16 January 2015.Retrieved27 May2012.
  6. ^abcAdams, Kye R.; Fetterplace, Lachlan C.; Davis, Andrew R.; Taylor, Matthew D.; Knott, Nathan A. (January 2018)."Sharks, rays and abortion: The prevalence of capture-induced parturition in elasmobranchs".Biological Conservation.217:11–27.doi:10.1016/j.biocon.2017.10.010.S2CID90834034.Archived fromthe originalon 2019-02-23.Retrieved2018-12-09.
  7. ^Stumpf, Sebastian; Kriwet, Jürgen (2019)."A new Pliensbachian elasmobranch (Vertebrata,Chondrichthyes) assemblage from Europe, and its contribution to the understanding of late Early Jurassic elasmobranch diversity and distributional patterns ".PalZ.93(4): 637–658.doi:10.1007/s12542-019-00451-4.
  8. ^"Chondrichthyes: Fossil Record".University of California Museum of Paleontology. U.C. Berkeley.
  9. ^Douady, C.J.; Dosay, M.; Shivji, M.S.; Stanhope, M.J. (2003). "Molecular phylogenetic evidence refuting the hypothesis of Batoidea (rays and skates) as derived sharks".Molecular Phylogenetics and Evolution.26(2): 215–221.doi:10.1016/S1055-7903(02)00333-0.PMID12565032.
  10. ^McEachran, J.D.; Aschliman, N. (2004). "Phylogeny of batoidea". In Carrier, J.C.; Musick, J.A.; Heithaus, M.R. (eds.).Biology of sharks and their relatives.Boca Raton, Florida: CRC Press. pp. 79–114.
  11. ^Kriwet, Jürgen."The systematic position of the Cretaceous sclerorhynchid sawfishes (Elasmobranchii, Pristiorajea)"(PDF).Archived fromthe original(PDF)on 2016-04-16.Retrieved2016-04-04.
  12. ^abNelson, J.S. (2006).Fishes of the World(fourth ed.). John Wiley. pp. 69–82.ISBN978-0-471-25031-9.
  13. ^abBullock, Theodore Holmes; Hopkins, Carl D.; Popper, Arthur N.; Fay, Richard R. (2005).Electroreception.Springer. pp. 5–7.ISBN978-0-387-23192-1.
  14. ^abFaria, Vicente V.; McDavitt, Matthew T.; Charvet, Patricia; Wiley, Tonya R.; Simpfendorfer, Colin A.; Naylor, Gavin J.P. (2013)."Species delineation and global population structure of critically endangered sawfishes (Pristidae)".Zoological Journal of the Linnean Society.167:136–164.doi:10.1111/j.1096-3642.2012.00872.x.
  15. ^Pacoureau, Nathan; Rigby, Cassandra L.; Kyne, Peter M.; Sherley, Richard B.; Winker, Henning; Carlson, John K.; Fordham, Sonja V.; Barreto, Rodrigo; Fernando, Daniel; Francis, Malcolm P.; Jabado, Rima W.; Herman, Katelyn B.; Liu, Kwang-Ming; Marshall, Andrea D.; Pollom, Riley A.; Romanov, Evgeny V.; Simpfendorfer, Colin A.; Yin, Jamie S.; Kindsvater, Holly K.; Dulvy, Nicholas K. (2021). "Half a century of global decline in oceanic sharks and rays".Nature.589(7843): 567–571.Bibcode:2021Natur.589..567P.doi:10.1038/s41586-020-03173-9.hdl:10871/124531.PMID33505035.S2CID231723355.
  16. ^Briggs, Helen (28 January 2021)."Extinction: 'Time is running out' to save sharks and rays".BBC News.Retrieved29 January2021.
  17. ^Richardson, Holly (27 January 2021)."Shark, ray populations have declined by 'alarming' 70 per cent since 1970s, study finds".ABC News.Australian Broadcasting Corporation.Retrieved29 January2021.
  18. ^Guide of Mediterranean Skates and Rays. Oct. 2022. Mendez L., Bacquet A. and F. Briand.[1]

Bibliography

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  • McEachran, J.D.; Dunn, K.A.; Miyake, T. (1996). "Interrelationships of the batoid fishes (Chondrichthyes: Batoidea)".Interrelationships of Fishes.Academic Press.
  • Nelson, Joseph S.(2006).Fishes of the World(4th, illustrated ed.). John Wiley & Sons.ISBN9780471756446.
[edit]
  • "Shark references".– database of bibliography of living/fossil sharks and rays (seeChondrichtyes: Selachii) with more than 15 000 listed papers and many download links.
  • "Rays Fact Sheet".Rays fact sheet(PDF).Fisheries (Report). Recreational fishing. Perth, Australia: Government of Western Australia. Archived fromthe original(PDF)on 13 May 2013.


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