4. Kingdom Animalia - part 10 - Phylum : Echinodermata

 


4. Kingdom Animalia - part 10 - Phylum : Echinodermata


Phylum : Echinodermata (Echinus - Spines, derma - skin)

  • e.g. Asterias (Sea star), Cucumaria (Sea cucumber), Echinus (Sea urchin), Antedon (sea lily), Ophiothrix (Brittle star).
  • These are exclusively marine, solitary, sedentary or free-living and gregarious, benthic.
  • These are radially symmetrical animals with pentamerous symmetry. 
  • Body may be spherical, elongated or star-shaped.
  • Endoskeleton is made up of calcareous ossicles.
  • Spines are present on the body, hence the name echinodermata. 
  • The body is without definite body divisions, instead, there are two sides as oral and aboral.
  • The peculiar character is presence of water vascular system in which water enters through madreporite. This system is used in locomotion, food capturing, respiration, etc. 
  • Digestive system is complete. 
  • Mouth is ventrally present on oral surface and anus on aboral surface.
  • Respiration is performed by peristomial gills, papillae, respiratory tree, etc. 
  • Circulatory system and excretory system is absent.
  • Nervous system is simple with a nerve ring around mouth and radial nerves in the arms. 
  • Sexes are separate (sometimes bisexual), fertilization is external, development is indirect.
  • They show high power of regeneration

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