Osteichthyes: Definition, Characteristics, Examples



Osteichthyes is a class of fish that consist of all the bony fish. These fishes are composed of bony endoskeleton and hence the name bony fish. These fishes are different from the rest of the classes of fishes in many characteristics. The main difference of characteristics between bony fish and cartilaginous fish is the presence of bone and cartilage respectively. Between the various classes of vertebrae, Osteichthyes is the largest class.

Characteristics of Osteichthyes

Following are the characteristics of Bony fish that separates them from other fish classes

Ostheichthyes characteristics

  • They have a streamlined body which accommodates their body while moving forward to filter the water friction.
  • Osteichthyes can be found in both marine and freshwater environment which makes them the abundant class of fishes.
  • As discussed above, the endoskeleton of bony fish is formed of bone compared to the cartilage endoskeleton of cartilaginous fishes.
  • Unlike cartilaginous fish that have their mouth ventrally located, bony fish have a terminal mouth.

Osteichthyes Terminal mouth

  • Osteichthyes have 4 pair of gill slit and each side is covered by an operculum.
  • They are cold-blooded, that is, poikilothermic.
  • Their skin is covered by cycloid/ctenoid scales.

Bony fish scales

  • They have developed air bladder, unlike cartilaginous fish in which they’re absent and they have to keep swimming.
  • Like all the other fish classes, Osteichthyes too have a two-chambered heart.
  • Bony fish have separate sex.
  • Fertilization is external and lay eggs, that is, oviparous.
  • They have direct development mode of life, that is, no larval stage is formed.

Example of Osthiechythyes

Following are some examples of Osthychthyes

  • Common Mola/ Ocean sunfish (Heaviest-known bony fish)

(M. Mola)

Common Mola

  • Catfish



  • clownfish



  • Tuna fish



  • Eel



  • Pufferfish



  • Tigerfish

(Hydrocynus vittatus)


  • Flatfish



  • Mudskipper



  • Needlefish



  • Flyingfish


flying Fish

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