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Why don't marine protozoa have contractile vacuoles?

Best Answers

The cells must be isotonic with seawater, else they would lose water. However, fresh water is hypotonic to cytoplasm, so a contractile vacuole adaptation becomes useful to pump out water in a freshwater environment. read more

Because salt cannot enter the vacuole to achieve equilibrium, water must leave. This will make the contractile vacuole useless and probably inactive. Also, fresh water organisms tend to be hyper-osmotic with too much water. The contractile vacuole rectifies this. read more

The salt content outside the vacuole will thus be much higher than in the contractile vacuole. Because salt cannot enter the vacuole to achieve equilibrium, water must leave. This will make the contractile vacuole useless and probably inactive. Also, fresh water organisms tend to be hyper-osmotic with too much water. read more

Marine protozoa do not have contractile vacuole unlike fresh water protozoa because of the reason that contractile vacuole is used to store and remove excess water (due to endosmosis) which if comes in rapidly can cause the cell to burst,As marine protozoa have a hypertonic external enviorment they do not possess a problem of excess endosmosis instead they have to conserve their water content from getting lost in enviorment. read more

Marine protozoa lives in a hypertonic environment unlike fresh water protozoa. Contractile vacuole is used to store and remove excess water which is due to endosmosis. Marine protozoa does not have contractile vacuole because of its need to conserve their water content from getting lost in their hypertonic environment. read more