Imagine walking around and being able to taste everything you walk across or everything you touch with your hands…Yuck! Well that is exactly what happens with all star fish or what researchers now call sea stars. All of their appendages are called arms and they can regrow them, which usually takes a couple of months, although some species can regrow them very quickly.

    Cardiac stomach
    Cardiac stomach and regrowth of an arm.

    On their arms they have hundreds and hundreds of tube feet which come in a variety of shapes and have different functions, like suction cups, or little shovels. The tube feet also act as the sea stars' tongues.

    Tube feet
    Small tube feet or the or the "tongues" of the starfish.

    In the sea star assay I am helping out with, with Maggie Amsler, we're feeding the extract pies (that I talked about in an earlier journal) to the sea stars to see if they like the taste of the chemical extract.

    Sea stars
    Our sea stars have developed a habit of telling us when they are hungry.

    We begin by placing a piece of pie midway down the arm, and using the tube feet the sea star either moves the pie towards its mouth, or pushes the pie off its arm if it doesn’t like the taste.

    Feeding
    Feeding the sea stars as part of the bio assay.

    To actually eat, the sea stars have two options because they have two stomachs. Cardiac, which they can send outside their body. So let's say they see a clam that is shut, they can send out their stomachs and work their way through the opening of the clam and start to digest it from the inside out.

    Pyloric stomach, which is the interior stomach, connects to the pyloric ceca which goes out to each one of the arms where it stays until it is used.

    Pyloric ceca
    Dissection of the pyloric ceca.

    Comments

    Kevin Dickerson

    How much cutting can a sea star take? If cut in half, will both halves regenerate?

    Keith Smith

    As long as part of the oral disk remains intact the parts will regenerate themselves. It was actually a big problem for fishermen who would bring them up in nets and cut them up to "kill" them and then throw them back, but unknowingly would be increasing their population.