Coelenterata : General Characters and Example

 Coelenterata : Defination 

• These are multi cellular aquatic animal with tissue grade level  of organisation having gastro vascular cavity.

General characters

• They are aquatic, mostly marine, sessile or free-swimming animals.

• They are Diploblastic, Acoelomate, radially symmetrical animal with tissue grade level of organisation.

• They are also called as  Cnidaria.The word cnidarian  has  been taken from the Cnidoblasts or cnidocytes. 

• Cnidoblasts contain the stinging capsules called as nematocysts which are  present on the tentacles and the body. 

• Cnidoblasts are used for the  anchorage, defense and for the capture of prey.

• Cnidarians have a central gastro-vascular cavity or Coelenteron with a single opening called mouth on hypostome.

• Digestion is extracellular and intracellular. 

• Some of the cnidarians are called as corals  because they have a skeleton composed of calcium carbonate. 

• Cnidarians also have  two basic  stage in their life cycle called polyp and medusa . 

• The polyp Is a sessile and cylindrical form like Hydra, Adamsia whereas, the Medusa is umbrella-shaped and free-swimming like Aurelia or jelly fish.

• Metagenesis is alternation of generation between polyp and Medusa in cnidarians.  

• Polyps reproduce asexually by budding  and form medusae. 

• Medusae form sperm and egg sexually and  form the polyps through the Fertilization externally.

Examples of Coelentreta 
1. Physalia

• It is commonly called as Portuguese man of war.

• It is marine neuston animal because it always float in ocean.

• During floating, it look like a warship therefore it is called as Portuguese man of war.

• It has pneumatophore which can be seen on water surface while floating and rest of body are submerged in water.

• Pneumatophores are composed of units called zooids which may be gonozooids and gastrozooids. These zooids may  have tentacles.

2. Adamsia

• It is commonly called as sea anemone.

• Body of Adamsia is divided into oral disc, column and pedal disc.

• It is found to be attached with molluscan shell by its Pedal disc.

• Oral disc has central mouth which is surrounded by the nematocyst bearing small tentacles.

• Adamsia and Hermit crab or clown fish show commensalism. Crab get protection from predator due to its stinging capsule.

• It is found in United States at North Carolina to Florida in shallow water.

  3. Pennatula

• It is commonly called as sea Pen or Sea feather.

• Body  is divided into distal rachis and peduncle.

• Rachis has fleshy branches with a series of 8 to 12 gastrozooids.

• It is sedentary and colonial animal and found in deep sea and prefer warm water.  

• Gastrozooids are feeding zooids and form gamete also Siphonozooids draw water current

• It is found in United States at  St. Lawrence to Carolina and also common in Europe.

4. Gorgonia 

• It is commonly called as sea Fan.

• It is a salt water invertebrate and can be identified by its purple color tissue and it's fan shape body.

• It's skeleton is made up of Collagen derivative compound called as Gorgonin and Calcite.

• It is tube like polyp  and protrude from needle like Spicules. 

• Gorgonia is sessile , Immobile and Colonial Animal and found to be attached with the surface.

• It is found in sea coast of West indies , Atlantic ocean and Madras Coast.

 5. Meandrina 

• It is commonly called as Brain Coral because it's shape resemble with the human brain.

• It is a colonial  coelenterate and look like polyp and secrete hard skeleton of calcium carbonate therefore called as stony coral.

• They use their tentacles to catch prey and as a defense organ.

• Brain Coral reproduce asexually  through buffing of polyp and sexually by sperm and egg .

• It is found in shallow warm water in coral reef through out the world like indo Pacific coast and Gulf of Mexico.