Phylum Coelenterata : General Characteristics and Classification


Gr., koilos : Hollow; enteron : intestine

General characters

  1. Metazoa with tissue grade of organization
  2. Aquatic : mostly marines few are freshwater forms, e.g. Hydras
  3. Sedentary or free swimming and colonial or solitary
  4. Radially symmetrical except sea-anemone which is bilaterally symmetrical
  5. Acoelomate
  6. Diploblastic metazoan
  7. Exclusively carnivorous, no herbivorous forms known
  8. Exhibit polymorphism ; polyp, medusa, and blastostyle structures are formed
  9. Individuals are known as zooids
  10. Anterior end of the body has hypostome on which mouth is present surrounded by tentacles. Anus is absent.
  11. Possess nematocyst; serve the function of paralyzing the prey by injecting poison or to hold the prey or used for adhesion.
  12. Digestion is intracellular, extracellular or both
  13. Reproduction both sexual and asexual (budding)
  14. Life-cycle exhibits alternation of generation or metagenesis


3 classes based on dominance of polyp or medusa forms


(Hydros: water ; zoios : animal)


(Gr., Skyphos=cup ; zoios=animal)


(Gr., Anthos=flower ; zoios=animal)

Mostly marine, some freshwaterExclusively marine and planktonicExclusively marine, solitary or colonial
 Have thick mesogloeaGastrovascular cavities have partitions called mesentries
Examples: Hydra, Obelia, Physalia, Porpita etc.Eg : Aurelia, RhizostomaEg: Metridium, Alcyonium, Fungia, Heliopora etc.


Binod G C

I'm Binod G C (MSc), a PhD candidate in cell and molecular biology who works as a biology educator and enjoys scientific blogging. My proclivity for blogging is intended to make notes and study materials more accessible to students.

Leave a Reply

Your email address will not be published. Required fields are marked *