They are pervasive and play many different roles in the marine environment, from being the base of the food chain, controlling much of the flow of marine energy and nutrients, and being essential to the ocean's health.
The water vascular system of a sea star enables movement, digestion and respiration through the use of water to exert force on limbs known as tube feet. The vascular system is primarily water but also contains coelomocytes, protein and potassium salts.
Cell type – prokaryotic or eukaryoticcell structure – cell wallnutrition – autotrophic or heterotrophicbody type – unicellular or multicellular
It is called a watershed.
