superorder of cartilaginous fishes, normally known as rays

Batoidea is a superorder of cartilaginous fishes, normally known as rays. They and their close relatives, the sharks, comprise the subclass Elasmobranchii. Rays are the largest group of cartilaginous fishes, with well over 600 species in 26 families. Rays are distinguished by their flatten bodies, enlarged pectoral fins that are fused to the head, and gill slits that are placed on their adaxial surfaces .

anatomy [edit ]

Batoids are flat-bodied, and, like sharks, are cartilaginous pisces, meaning they have a boneless skeleton made of a tough, elastic cartilage. Most batoids have five ventral slot-like body openings called gill slits that lead from the gills, but the Hexatrygonidae have six. [ 2 ] Batoid gill slits lie under the pectoral fins on the bottom, whereas a shark ‘s are on the sides of the head. Most batoids have a flat, disk-like soundbox, with the exception of the guitarfishes and sawfishes, while most sharks have a fusiform body. many species of batoid have developed their pectoral fins into broad flat wing-like appendages. The anal fin is lacking. The eyes and spiracles are located on acme of the principal. Batoids have a ventrally located mouth and can well protrude their upper yack ( palatoquadrate cartilage ) away from the cranium to capture prey. [ 3 ] The jaws have euhyostylic type suspension, which relies completely on the hyomandibular cartilages for patronize. [ 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 [edit ]

Batoids reproduce in a issue of ways. As is characteristic of elasmobranch, batoids undergo inner 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 ] All skates and some rays are oviparous ( egg laying ) while other rays are ovoviviparous, meaning that they give birth to young which develop in a uterus but without involvement of a placenta. [ 6 ] The eggs of oviparous skates are laid in coriaceous egg cases that are normally known as mermaid ‘s purses and which often wash up empty on beaches in areas where skates are common. Capture-induced premature birth and abortion ( jointly called capture-induced parturition ) occurs frequently in sharks and rays when fished. [ 6 ] Capture-induced parturition is rarely considered in fisheries management despite being shown to occur in at least 12 % of populate bear sharks and rays ( 88 species to date ). [ 6 ]

habitat [edit ]

Most species live on the sea floor, in a variety show of geographic regions – chiefly in coastal waters, although some live in deep waters to at least 3,000 metres ( 9,800 foot ). Most batoids have a cosmopolitan distribution, preferring tropical and subtropical marine environments, although there are moderate and cold-water species. alone a few species, like manta rays, live in the open ocean, and only a few live in fresh water, while some batoids can live in brackish bays and estuaries .

Feeding [edit ]

Most batoids have developed clayey, rounded tooth for crushing the shells of bottom-dwelling species such as snails, clams, oysters, crustaceans, and some fish, depending on the species. Manta rays feed on plankton .

evolution [edit ]

Batoids belong to the ancient descent of cartilaginous fishes. Fossil denticles ( tooth-like scales in the skin ) resembling those of today ‘s chondrichthyans date at least as far back as the Ordovician, with the oldest unambiguous fossils of cartilaginous pisces date from the middle Devonian. A clade within this divers kin, the Neoselachii, emerged by the Triassic, with the best-understood neoselachian fossils dating from the Jurassic. The oldest confirm ray is Antiquaobatis, from the Pliensbachian of Germany. [ 8 ] The clade is represented today by sharks, sawfish, rays and skates. [ 9 ]

categorization [edit ]

The classification of batoids is presently undergo rewrite ; however, molecular evidence refutes the guess that skates and rays are derived sharks. [ 10 ] Nelson ‘s 2006 Fishes of the World recognizes four orders. The Mesozoic Sclerorhynchoidea are basal or incertae sedis ; they show features of the Rajiformes but have snouts resembling those of sawfishes. however, attest indicates they are probably the sister group to sawfishes. [ 11 ] Phylogenetic tree of Batoidea : [ 12 ]

Order Image Common name Family Genera Species Comment
Total CR IUCN 3 1.svg EN IUCN 3 1.svg VU IUCN 3 1.svg
Myliobatiformes Myliobatis aquila sasrája.jpg Stingrays and relatives 10 29 223 1 16 33 [a][13]
Rajiformes Amblyraja hyperborea1.jpg Skates and relatives 5 36 270 4 12 26 [b]
Torpediniformes Torpedo torpedo corsica2.jpg Electric rays 4 12 69 2 9 [c][14]
Rhinopristiformes Sawfish genova.jpg Shovelnose rays and relatives 1 2 5-7 3-5 2 [d][15]

Order Torpediniformes

  • Family Hypnidae (coffin rays)
  • Family Narcinidae (numbfishes)
  • Family Narkidae (sleeper rays)
  • Family Torpedinidae (torpedo rays)

Order Rhinopristiformes

  • Family Glaucostegidae (giant guitarfishes)
  • Family Platyrhinidae* (fanrays)
  • Family Pristidae (sawfishes)
  • Family Rhinidae (wedgefishes)
  • Family Rhinobatidae (guitarfishes)
  • Family Trygonorrhinidae (banjo rays)
  • Family Zanobatidae* (panrays)

* the placement of these families is unsealed

Order Rajiformes

  • Family Anacanthobatidae (legskates)
  • Family Arhynchobatidae (softnose skates)
  • Family Gurgesiellidae (pygmy skates)
  • Family Rajidae (skates)

Order Myliobatiformes

  • Family Aetobatidae (pelagic eagle rays)
  • Family Dasyatidae (whiptail stingrays)
  • Family Gymnuridae (butterfly rays)
  • Family Hexatrygonidae (sixgill stingrays)
  • Family Myliobatidae (devilrays)
  • Family Plesiobatidae (giant stingarees)
  • Family Potamotrygonidae (Neotropical stingrays)
  • Family Rhinopteridae (cownose rays)
  • Family Urolophidae (stingarees)
  • Family Urotrygonidae (round stingrays)

conservation [edit ]

According to a 2021 survey in Nature, the number of oceanic sharks and rays has declined globally by 71 % over the preceding 50 years, jeopardising “ the health of entire ocean ecosystem ampere well as food security for some of the world ‘s hapless countries ”. Overfishing has increased the global extinction risk of these species to the point where three-quarters are now threatened with extinction. [ 16 ] [ 17 ] [ 18 ]

Differences between sharks and rays [edit ]

All sharks and rays are cartilaginous fishes, contrasting with osseous fishes. many rays are adapted for feeding on the buttocks. Guitarfishes are reasonably between sharks and rays, displaying characteristics of both ( though they are classified as rays ) .

See besides [edit ]

References [edit ]

bibliography [edit ]

  • “Shark references”. – database of bibliography of living/fossil sharks and rays (see Chondrichtyes: 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 from the original ( PDF ) on 13 May 2013.