Contractile vacuoles are subcellular organelles that play vital roles in osmoregulation and excretion.
These organelles help in expelling out the excess water from the cell thereby maintaining an intracellular balance of water. This helps the organism survive hypotonic conditions.
They are found in aquatic protists such as Amoeba, Euglena, paramecium, etc.
Contractile vacuoles are permanent structures that help in maintaining water balance in the cell.