What has hydroskeleton?

A hydroskeleton, or hydrostatic skeleton, is a structural support system found in certain animals, particularly in soft-bodied organisms like jellyfish, worms, and some mollusks. It relies on the pressure of fluid within a body cavity to maintain shape and enable movement. When the fluid is contained within a flexible outer membrane, it allows the organism to change shape and move by contracting and relaxing muscles. This system is crucial for locomotion and provides support without the rigidity of a traditional skeleton.