General Characters, Examples of Phylum Cyclostomata

 

Defination 

• Cyclostomata are primitive vertebrates and having circular mouth 👄 but absence of jaws.

General Characters 

• All members of cyclostomes are ectoparasite on some fish 🐟.

• They have elongated body with six to fifteen pairs of gills slits for  respiration 🫁.

• They have circular and sucking mouth  👄 without jaw.

• Body is not covered by the scales ♎ and paired fins are absent.

• Notochord is replaced by the cartilaginous vertebral column. Cranium is also cartilaginous.

• Heart has two chambers and circulatory  system is closed type.

• Animals are marine but migrated into fresh water for spawning. After spawning they die after few days and their larva return to ocean after metamorphosis.

• Mouth bear teeth and moved by protractor and retractor muscles.

• Digestive system has no stomach and oesophagus is directly open into intestine.

• Brain is well developed with 10 pair of cranial nerve.

• A pair of mesonephric kidney are present for the Excretion.

• Life cycle of cyclostomes have Ammocoeate larva which is transformed in to adult after metamorphosis.

Example of Cyclostomata 

Petromyzon

• It is commonly called as lamprey.

• Body is elongated. Mouth is circular and sucking with large and sharp teeth.

• Skin is soft, smooth without scales but  has with unicellular mucus gland on skin.

• It has no paired fin but a median fin is present.

• It has six to fifteen pairs of gills slits for respiration.

• Lamprey are ectoparasite on some large fish.

• It is migrated into fresh water for spawning. After spawning they die after few days .

• Vertebral column and  Cranium is cartilaginous.

• Circulatory system is closed.

Myxiene

• It is commonly called as Hag fish and exclusively marine.

• Body is elongated. Mouth  terminal , circular and sucking without eyes and jaws.

• Hagfish release slime which affect respiratory system of their predator.

• It has no dorsal  fin or reduced dorsal fin.

• It has six to fifteen pairs of gills slits for respiration on both side of body.

• Hag fish has primitive brain and reduced pineal body.

• It is migrated into fresh water for spawning. After spawning they die after few days .

• Vertebral column and  Cranium is cartilaginous.

• Circulatory system is closed.