What is the primary movement method of a medusa?

The primary movement method of a medusa is indeed through swimming via the contraction of its bell structure. Medusae, commonly known as jellyfish, have a distinctive umbrella-shaped bell that allows them to move through the water effectively. When the bell contracts, it pushes water behind them, creating a jet propulsion effect that propels the medusa forward. This mode of movement is efficient for navigating through their aquatic environment, allowing them to travel to different areas in search of food or to evade predators.

Other methods of movement mentioned, such as using cilia or remaining anchored to a surface, do not apply to medusae as they do not possess the necessary anatomical features for these actions. Medusae typically do not have the ability to remain anchored; they are free-swimming organisms. Additionally, while some creatures may contort their bodies for rapid movement, medusae specifically utilize their bell's contraction for swimming, distinguishing their movement strategy from that of other aquatic animals.