10. Circulatory system: Perihaemel blood vascular system. Each radial canal gives a branch to the buccal podia and terminates as the lumen of the terminal tentacle. (iii) The water-vascular system has soft membranes. Developed coelom and have a water driven tube system (water vascular system). Excretory system – absent. The visual system of starfish. 9. It allows diffusion of respiratory and nitrogenous wastes across the body wall. Tube feet for locomotion and have regeneration capacity. 7. Functions of the water vascular system (i) The water-vascular system is chiefly used for locomotion. 4. Sub Phylum: Echinozoa. An excretory system is absent. Reproduction – Dioecious animals , Reproduction is sexual. Fig: Asterias and Ophiura. Alimentary canal: Straight or coiled. (4)It works like hydraulic system. (B) The arm tip of the crown-of-thorns starfish, A. planci showing a similar arrangement as for Culcita novaguineae. (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. Above: a transverse (cross) section through the arm of the brittlestar Ophiura. Tube feet (podia) participate in locomotion, gas … It uses hydraulic pressure and the action of muscles to operate the various podia (Brusca and Brusca 1990). The most distinctive feature of echinoderms is the presence of water vascular system which helps in locomotion, capture and transport of food and respiration. Madriporite and anus remain on the aboral surface. 8. Helps in locomotion, capture and transport of food and respiration. (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). Water vascular system – distinctive feature. Locomotion: Water vascular system with podia and tube-feet madreporite mostly present. (ii) The original function of water-vascular systems was feeding, not locomotion. The water vascular system is a complex network of canals and reservoirs. The main ring canal bears five small inter-radial Tiedemann’s bodies. Hemal system. Water Vascular System of Echinus: The water vascular system is fundamen­tally similar to that of Asterias. (6) When the muscles in the tube feet contract the tube … Reproduction: Sexual and gonochoristic. The podia also function in gas exchange and sensory reception. 7. Podia include both tube feet (used in locomotion and attachment) and tentacles (used in feeding). 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. 11. Fertilisation – usually external. Radially symmetrical, globoid or discoid without arms or brachioles. Echinoderm - Echinoderm - Form and function of external features: Echinoderms have a skeleton composed of numerous plates of mineral calcium carbonate (calcite). ... For example, Ophiura. (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. Sexes are separate. Digestive system – complete with mouth on the lower (ventral) side and anus on the upper (dorsal) side. (5) Water enters the Water Vascular System through a madreporite. Digestive system is complete with mouth on the lower (ventral) side and anus on the upper (dorsal) side. 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. The water vascular system is a unique and defining characteristic of echinoderms. The stone canal is membranous and is not calcified. 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