General Characters of Cephalochordata : Amphioxus

 Defination 

• Cephalochordates are put under sub phylum of Chordata fish like,filter feeder and marine animals included Amphioxus or lancelet.

General Characters 

• They are mostly marine, fish like, segmented with elongated body.

• Alimentary canal is long with pharynx and gills slits with ciliary mode of feeding.

• Dorsal, caudal and ventral fins are present. 

• Notochord is present from head to tail and remain present through out the life.

• Protonephredia and Solenoacytes  are excretory organ.

• Two pair of cerebral nerve and several pairs of spinal nerve are present.

• Respiration takes place through gills slits are also present.

• Coelom is enterocoelic.

• Saxes are separe. Gonads are present without gonoduct.Fertilisation is external.

• Body is eel like and well adapted for burrowing .

• They have an endostyle in their pharynx for filter feeding.

• Reproduction is mostly sexual. Asexual reproduction is absent.

• Circulatory system is closed.Brain is absent.

Example of Cephalochordata 

Amphioxus 

• It is also called as Branchiostoma or Lamprey.

• It has dorsal nerve cord, Notochord , gills slits and post anal tail.

• It has a wide mouth at trunk ,anus on caudal fin and atriopore.

• Mostly they are burrowing but they can swim by the myotomes.

• A wheel organ or muller organ is present in epithelium of oral cavity help in feeding mechanism.

• Digestive process is present but digestion take place through phagocytosis.

• Circulatory system is closed . Blood is colourless and devoid of respiratory pigment and corpuscles.

• Amphioxus has endostyle which is similar to thyroid glands.

• Excretory organ are protonephredia contain numerous Solenoacytes