Final answer:
Brittle stars have long, thin and flexible arms that are sharply delineated from the central disk. They use their arms for locomotion and prey capture.
Step-by-step explanation:
Brittle stars, which belong to the class Ophiuroidea, have long, thin, and flexible arms that are sharply delineated from the central disk. Unlike sea stars, brittle stars do not have plump arms.
These flexible arms allow brittle stars to move by lashing them out or wrapping them around objects and pulling themselves forward. The arms of brittle stars are also used for grasping prey.
Overall, the arms of brittle stars are both sharply delineated from the central disk and flexible, enabling them to perform various functions such as locomotion and prey capture.