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Tuesday, September 29, 2020

Class Osteichthyes - NEET-Biology

Class Osteichthyes

Fig: Catla fish 

  • The vast majority of vertebrates belong to a superclass of gnathostomes called Osteichthyes.
  • Unlike chondrichthyans, nearly all living osteichthyans have an ossified (bony) endoskeleton with a hard matrix of calcium phosphate [Ca3(PO4)2].


Important characteristics:

  • It includes both marine & freshwater fishes with a bony endoskeleton.
  • They have four pairs of gills that are covered by an operculum on each side.
  • The heart is two-chambered (one auricle & one ventricle).
  • Most fishes can control their buoyancy with an air bladder known as the swim bladder. 
  • Adult kidneys are mesonephric. Excretion is chiefly ammonetelic.
  • They are cold-blooded animals.
  • Sexes are separate. Fertilization is usually external.
  • Mostly oviparous, rarely ovoviviparous or viviparous.
  • Development direct, rarely with metamorphosis.
  • Examples: Latimeria (Lobe-finned fish), Dipnoi (Lung-fish), Hippocampus (Sea-horse), Exocoetus (Flying fish), Echeneis or Remoro (Suckerfish), Anguilla (eel), Anabas (Climbing perch), Catla-Catla (Catla), Pterophyllum (Angelfish), Betta (Fighting fish).
Fig: Dipnoi (Lung-fish)


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