Digestive system – complete with mouth on the lower (ventral) side and anus on the upper (dorsal) side. An excretory system is absent. 7. Tube feet (podia) participate in locomotion, gas … Reproduction: Sexual and gonochoristic. The stone canal is membranous and is not calcified. Body coelom: Enterocoelic type includes perivisceral coelom and water vascular cavities. It allows diffusion of respiratory and nitrogenous wastes across the body wall. Above: a transverse (cross) section through the arm of the brittlestar Ophiura. 4. Alimentary canal: Straight or coiled. The water vascular system is a hydraulic system used by echinoderms, such as sea stars and sea urchins, for locomotion, food and waste transportation, and respiration. Hemal system. The visual system of starfish. Reproduction – Dioecious animals , Reproduction is sexual. (A) The distal part of the ambulaccecral grove of the cushion star, Culcita novaguineae, showing the distalmost tube foot (DmTF) holding the eye and the putative sensory tube feet (white arrows). Radially symmetrical, globoid or discoid without arms or brachioles. (ii) The digestive system in Platyhelminthes has only a single opening to the outside of the body that serve as both mouth and anus, and is hence called complete. It is a vital part of the system and exhibits control over the hundreds to thousands of tube feet that live in the ambulacral grooves. 7. Developed coelom and have a water driven tube system (water vascular system). The main ring canal bears five small inter-radial Tiedemann’s bodies. Madriporite and anus remain on the aboral surface. ... For example, Ophiura. 10. (iii) In open type of circulatory system, the blood is pumped out of the heart and the cells and tissues are directly bathed in it. (4)It works like hydraulic system. The podia also function in gas exchange and sensory reception. It uses hydraulic pressure and the action of muscles to operate the various podia (Brusca and Brusca 1990). Functions of the water vascular system (i) The water-vascular system is chiefly used for locomotion. Sub Phylum: Echinozoa. Water vascular system – distinctive feature. Locomotion: Water vascular system with podia and tube-feet madreporite mostly present. Excretory system – absent. Digestive system is complete with mouth on the lower (ventral) side and anus on the upper (dorsal) side. Tube feet for locomotion and have regeneration capacity. 11. Sexes are separate. Each radial canal gives a branch to the buccal podia and terminates as the lumen of the terminal tentacle. Circulatory system: Perihaemel blood vascular system. Helps in locomotion, capture and transport of food and respiration. (6) When the muscles in the tube feet contract the tube … Water Vascular System of Echinus: The water vascular system is fundamen­tally similar to that of Asterias. Fig: Asterias and Ophiura. (B) The arm tip of the crown-of-thorns starfish, A. planci showing a similar arrangement as for Culcita novaguineae. 9. Echinoderm - Echinoderm - Form and function of external features: Echinoderms have a skeleton composed of numerous plates of mineral calcium carbonate (calcite). (ii) The original function of water-vascular systems was feeding, not locomotion. The water vascular system is a unique and defining characteristic of echinoderms. 8. (iii) The water-vascular system has soft membranes. Fertilisation – usually external. Podia include both tube feet (used in locomotion and attachment) and tentacles (used in feeding). (5) Water enters the Water Vascular System through a madreporite. 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