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| Phylum Echinodermata |
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 Free living exclusively marine forms. |
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 Adults are radially symmetrical while larvae are bilaterally symmetrical. |
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 Body is represented by a central disc covered by ossicles with spines called pedicellaria. |
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 Disc may bear extensions called arms. |
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 Digestive system is complete. |
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 A unique ambulacral or water vascular system is present. |
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 Tube feet are present for locomotion and respiration. Tube feet are extended and retracted by variation in hydraulic pressure of the fluid in them and contraction of their muscles. |
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 Nervous system has a central nerve ring with five radiating nerves. |
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 Reproduction is sexual. Sexes are separate. Development is indirect. |
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 Show very high power of regeneration. |
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 Tube feet are for feeding as well. |
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| fig. 10.20 - Examples of Echinodermata |
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| The phylum is divided into five classes. |
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| fig. 10.21 - Starfish Anatomy |
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