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Sea star's water vascular system enable them through the process of feeding, locomotion, and respiration.

Interesting Fact:

Star fish does not have a brain and does not function under a global sensory motor. Its locomotion is completely dependent on the interaction between the environment and individual body parts.

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Animal behaviors are usually described by two models of movement: insect flight is enabled through sensory feedback being communicated through a central processing system, or a completely decentralized individual response to sensory information such as fish or ant colony.

None of which completely describes sea star. Information needs to be communicated mechanically between the feet as they sense its own state and respond accordingly.

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Synchronization, Autonomy

Any one foot can act autonomously when reacting to stimuli.When all the feet are synchronized, they can product a bouncing motion. A "dominant arm" determines the direction while integrating localized responses from other feet.

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How does sea star move mechanically?

Vascular system within sea star plays a major role in its ability to move. The water first moves from the environment into the Madreporite which is then channeled by the stone canal to the ring canal. The ring canal then distributes the water to the radial canals. Apullaes are connected to the radial canal; it's a muscular sack that contract as water move through and translates the increased pressure into elongation of the feet and making the the organized stepping movement possible.