In freshwater protists, osmoregulation is taken care of by contractile vacuoles which absorb excess water in the cell and then excrete the water back into the environment. Osmoregulation is less important in saltwater protists. Difference between asexual and sexual reproduction. Most protists, especially ciliates, go through two types of reproduction. Environmental conditions usually dictates what type is used.
Binary fission is a type of asexual reproduction common during good environmental conditions.
Conjugation is a type of sexual reproduction common during stressful environmental conditions.