An analysis of water flow in tube living animals

Abstract Water flow has been studied in six tube-dwelling animals that have different pumping mechanisms and layout of their tube systems. The characteristics of the pumping mechanisms and the resistance of the tube systems have been found. Cilia act as impeller pumps and can produce large rates of flow when arranged in parallel, but may produce sufficient flow for small, long thin bodied animals when arranged in series. Larger vermiform animals must use piston mechanism to produce sufficient rates of flow and the high pressures they can produce do not seem to be of use to the animals during normal pumping. Animals with rigid limbs can use these to impel water and produce high rates of flow. Echinocardium , which has a globular body, must match the flow at the inflow and outflow points on the test to the flow over the circumference and has special ciliated spines at these sites to boost flow.