Coelenterata(Cnidaria)

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Coelenterata(Cnidaria) Dr.Suman Pawar R.K.M.M.Ahmednagar General Characters- . Aquatic,mostly marine, some are freshwater forms. Multicellular, diploblastic with outer ectoderm & inner endoderm,acoelomate animals with tissue grade of body organisation. Sedentary or free swimming forms. Solitary or colonial,radially symmetrical animals. Presence of slender & short tentacles provided with nematocysts which are the organs of offence & defense. The coelenterates show polymorphism as their zooids shows two forms i.e. polyp & medusa. The polyps are sessile & asexual zooids while the medusae are free living & sexual forms. They are carnivorous ,without anus, respiratory ,circulatory & exceretary system. Reproduction by sexual as well as asexual method. Life cycle shows alternation of generation as the asexual polypoid gen. is alternated with the sexual medusoid generation. Examples-Hydra,Physellia,Aurelia,Sea anemone. Classification of Phylum Coelenterata--- . Coelenterata--- . Classes--- 1-Hydrozoa e.g.-Hydra . 2-Scyphozoa e.g.- Cyanea . 3- Anthozoa e.g.-Sea anemone Sea anemone Cyanea Distinguishing Characters of Class-Hydrozoa-- . They are aquatic,marine & fresh water forms. Solitary or colonial forms. Life cycle includes both polyp & medusa Stages. Medusa with a true velum. Presence of non-cellular mesoglea. Gastrovascular cavity without stomodium . Gonads epidermal in origin. Ex.Hydra, Physalia. Physalia Distinguishing Characters of Class-Scyphozoa-- . Solitary marine forms. Dominant medusa stage in life cycle. Polyp reduced or absent. Presence of cellular mesoglea. No distinct velum in medusa. Ex.Aurelia, Pelagia. Aurelia (jelly fish) Cyanea (jelly fish ) Distinguishing Characters of Class- Anthozoa-- . Exclusively marine. Commonly called sea-flowers. Solitary or colonial. Life cycle with only polyp stage. Medusa stage absent. Gastrovascular cavity with mesenteries &nematocysts. Presence of cellular mesoglea. Presence or absence of calcarious skeleton. Ex. Tubipora,Adamsia Various Anthozoa Adamsia (Sea anemone) Corals.

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