Protozoans representing contractile-pulsatile-vacuoles

Question

Are protozoans representing contractile, or pulsatile, vacuoles simply found in fresh or in salt water?

Answer 1

Fresh water is less concentrated of solutes than sea water and it (that is, fresh water) tends to be less concentrated than the intracellular environment forming cells to swell. Sea water, on the other hand, as it is very concentrated tends to dehydrate the cell.

The vacuoles of protozoans are inner structures specialized in water storage which when essential release water to the cytoplasm. Vacuoles therefore can dilute the cytoplasm for it to enter into the osmotic equilibrium with environment. Protozoans of fresh water then require vacuoles more as their intracellular is hypertonic in association to the exterior. Without dilution mechanism given by the vacuoles, protozoans of fresh water would absorb plenty of water and would die.