Final answer:
Euryhaline polychaetes can tolerate a wide range of salinities, making them adaptable to different environments such as freshwater, marine, and brackish water conditions.
Step-by-step explanation:
Euryhaline polychaetes can tolerate a wide range of salinities. This means that they can survive in both freshwater and marine environments, as well as brackish water conditions. For example, some polychaetes are adapted to live in estuaries, where the salinity varies due to the mixing of fresh water and salt water. They have physiological adaptations that allow them to cope with changes in salinity.