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Friday, 27 January 2017

Animal Kingdom : Class Cyclostomata

Class Cyclostomata (Circular mouthed fishes)

  • They are ectoparasites on some fishes. Having sucking and circular mouth without jaws.
  • Body devoid of scales, gill slits for respiration, cranium and vertebral column is cartilaginous.
  • Circulation is closed type. They are marine but migrate to fresh water for spawning and die after few days. Larva return to seas after metamorphosis.
  • Example- Petromyzon (Lamprey), Maxine (Hag fish).

Class Chondrichithyes ( The Cartilaginous Fish)
  • They are marine, streamlined body, bears cartilaginous endoskeleton, cold blooded, tough skin with minute placoid scales.
  • Gill slits are separate with operculum, powerful jaw and predator.
  • Air bladder is absent, to avoid sinking swims constantly. Heart is two chambered, cold blooded (Poikalothermous)
  • Sexes separate, in males pelvic fins bears claspers. Internal fertilisation, many are viviparous.
             Electric organ is present in Torpedo and Poison sting in Trygon

             Example- Scoliodon (Dog fish), Carcharodron (great white shark).


Class Ostechthyes (The body fish)

·    Marine and fresh water both with bony endoskeleton. Streamlined body with four pair of gills covered by operculum.

·   Skin is covered with scales, air bladder is present, and heart is two chambered, cold blooded.
·    Sexes are separate, fertilisation external, oviparous and development direct.

Example : Marine- Hippocampus (Sea horse), Exocoetus (Flying fish). Fresh water- Labeo (Rohu), Catla , Clarias (Magur).

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