How does the body cavity help starfish?

1. Support: The body cavity provides structural support to the starfish's body. The fluid-filled cavity exerts hydrostatic pressure, which helps maintain the starfish's shape and rigidity.

2. Locomotion: The body cavity plays a crucial role in starfish locomotion. The water vascular system, which is part of the body cavity, consists of radial canals, ring canal, and tube feet. When water is pumped into the tube feet, they extend and attach to surfaces, allowing the starfish to move by pulling itself forward.

3. Feeding: The body cavity is involved in the starfish's feeding process. The cardiac stomach, located in the body cavity, everts out through the mouth to engulf prey. The digestive enzymes break down the food within the cardiac stomach, and the nutrients are absorbed into the body cavity.

4. Respiration: The body cavity also facilitates respiration in starfish. The thin-walled structures, such as papulae and gills, located on the surface of the body cavity, allow for the exchange of gases between the body fluids and the surrounding water.

5. Reproduction: In some starfish species, the gonads (ovaries and testes) are located within the body cavity. During the reproductive season, gametes are released into the body cavity and then expelled through the gonopores to the external environment for fertilization.

Overall, the body cavity serves multiple functions in starfish, including providing structural support, aiding in locomotion, facilitating feeding, enabling respiration, and playing a role in reproduction.