The general characteristic of Coelenterata are as follows :
1. Habitat : They are aquatic, most of them are marine and some are fresh-water. They are mostly sessile and some are free living. Few are active swimming or free floating like Aurelia.2. Body organization : They are multicellular organism with tissue grade of organizarion.
3. Symmetry : They are bilaterally or radially symmetrical with central gastovascular cavity.
4. Locomotion : Their locomotion is bought about by smmoth muscle fibre. Some like corals and metridium remain fixed on substratum.
5. Excrerition and repiration takes place through general body surface.
6. Reproduction : They reproduce asexually by budding, fission, and fragmentation.
7. They exhibit polymorphism :
polyp : asexuall form
medusa : sexuall form
Sexuall form is monoecious and dioecious.
The classification of phyllum Coelenterata is given below :
1. Hydrozoa
 |
| Hyrda |
a. They are mostly marine , few are freshwater form.
b. Both poly and medusa form is present in them.
c. Mesogloea is simple and non-cellular.
eg : hydra, obelia , physalia etc.
2. Scyphozoa
 |
| Aurelia |
a. They are exclusively marine.
b. Medusa form is dominant and polyp form is either reduced or absent.
c. Mesogloea is cellular.
eg : aurelia (jelly fish) , rhizostome
3. Anthozoa
 |
| Corals |
a. They are also exclusively marine.
b. Only polyp form is present and mwdusa form is absent in them.
c. Mesogloea has fibrous connective and amoeboid cells.
eg : metridium (sea-anemone) , corals etc
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