Two species of sea anemones, Metridium senile and Anthopleura xanthogrammica, illustrate the sorts of compromises made by sessile organisms between maximizing the transport done and minimizing the mechanical forces caused by flow.

  1. 1.

    M. senile occur in calm areas, but because they are tall, they are exposed to mainstream current velocities. Although A. xanthogrammica occur in areas exposed to wave action, they are short and effectively hidden from mainstream velocities.

  2. 2.

    Measurements of drag forces on anemones and models in a flow tank and in the field indicate that the shapes, sizes, flexibilities, and behaviours of anemones affect the flow forces they encounter.

  3. 3.

    Although M. senile and A. xanthogrammica occur in different flow habitats, the drag force on an individual of either species is about 1 N.

  4. 4.

    The water currents encountered by these anemones and their mechanical responses to the currents can be related to the manner in which the anemones harvest food from flowing water.

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