The water-vascular system of E. troschelii is unique to echinoderms and consists of canals and appendages of the body wall.  The entire system is derived from the coelom and the canals are thus lined with a ciliated epithelium and filled with fluid.  This is a well-developed system and also functions as a means of locomotion.  The entire water-vascular system is filled with fluid that is similar to seawater.  The system operates during locomotion as a hydraulic system.  The system connects to the outside through a series of pores called madreporites. They are covered in cilia to prevent large particles such as sand and other debris from clogging the openings.  It is this same system that helps E. troschelii right itself if it is turned over and climb up vertical substratum.