WATER VASCULAR SYSTEM.pptx

WATER VASCULAR SYSTEM- Animal kingdom

1. WATER VASCULAR SYSTEM/AMBULACRAL SYSTEM IN ECHINODERMS System of canals & associated structure filled with watery fluid containing Entire system derived from the coelom ( hydrocoel ), the canals are lined by ciliated epithelium. Basic components : madreporite , stone canal, ring canal, radial canal and tube feet It is variously modified in the different classes of echinodermata .

2. Water Vascular System in Asteroidea Components Madreporite - Hard, circular, porous, calcareous plate Found on the aboral surface of the disc inter- radially . Surface carries a number of radiating narrow furrows /grooves. Bottom of these grooves are perforated by minute pores. Each pore leads into a pore canal. Pore canals in turn unite to form several collecting canals which open into a small sac-like ampulla below. Ampulla leads into the stone canal.

3. Stone Canal : S-shaped canal extending from the madreporite to the ring canal. Wall strengthened calcareous rings lumen of the canal is divided by a longitudinal ridge. Ring Canal : Ring canal is a wide pentagonal canal lying around the oesophagus . Polian Vesicles : ring canal bears on its outerside five, thin walled, flask shaped, contractile structures called Polian vesicles. They store sea water help to regulate hydrostatic pressure inside the system by quickly emptying the water.

4. Tiedemann's Bodies/ Racemose Glands: Small, rounded, yellowish, glandular bodies Lymphatic glands involved in the production of corpuscles found in the water vascular system. Radial Canals : 5 radial canals arise from the five angles of the ring canal externally. Each radial canal runs into an arm above the ambulacral groove and terminates in a short tentacle at the tip. Lateral Canals: In each arm, the radial canal gives out on its lateral sides two rows of short, narrow, branches called lateral canals. Each lateral canal carries a tube feet at its tip. Lateral canals are provided with valves which prevent flow of water back to the radial canal. The valves are placed at the junction of lateral canal and ampulla .

5. Tube feet: Elastic,thin walled,hollow closed cylinderlike structure Three distinct region : ampulla,podum adhesive disc Ampulla - upper rounded sac like part of the tube foot Podium- middle tubular part Adhesive disc – terminal cup like part

6. Water Vascular System in Ophiuroidea Madreporite : oral in position & usually bears a single pore canal. Stone canal: runs upward to join the ring canal. Ring canal : situated in a grove on the aboral side ofthe jaw apparatus. Ring canal gives off polian vesicles in each interradius except the one which bears the stone canal. Polian vesicles are accompanied by long, slender, tubular appendages of unknown function, known as simroth's appendages. Tiedemann's bodies are absent. V-shaped lateral canals originate from the radial canals and terminate in tube Tube feet are poorly developed without ampulla and sucker.

7. Water Vascular System in Class Echinoidea Madreporite - aboral and leads to a ventral sinus through many pore canals. Stone canal descend orally to join the ring canal. Ring canal lies just above the masticatory apparatus ( aristotle's lantern). Five polian vesicles and five tiedemann's bodies present. Radial canals rise up to run along the under side of ambulacral areas of the test. Radial canal gives off lateral canals alternatively on both sides. Each tube foot consists of ampulla , podium and sucker.

8. Water vascular system in holothuroidea Madreporite lies in the coelom and does not communicate with the exterior. Stone canal usually divided into a bunch of smaller canals, extending between madreporite and ring canal. Ring canal encircles the pharynx. Number of polian vesicle –one Tiedemann's bodies absent. Five radial canals arise from the ring canal and run anterior wards. Tube feet on the ventral side are provided with suckers , used for locomotion, while those on the dorsal side are without suckers and probably sensory in function. In apoda , tube feet are absent, water vascular system is limited to the water ring, polian vesicle and buccal podia (tentacles).

9. Water Vascular System in Crinoidea Madreporite is absent. Ring canal encircling the mouth gives off stone canals hanging freely in the coelom . 5 radial canals originate from the ring canal. Each radial canal after entering an arm bifurcates and divides to supply all of the branches and pinnules . Lateral canals originating from the radial canals supply the tube feet. Tube feet lack ampullae and suckers and are covered with cilia Tegmen is perforated ciliated, funnel shaped water pores (ciliated funnels) that open into the coelom internally. Tiedemann's bodies and polian vesicles are absent.

10. Functions of Water Vascular System Locomotion: musculature provides a hydraulic pressure mechanism responsible for movement. The wall of ampulla is formed mainly of circular muscles while that of podium comprises longitudinal muscles. filled with a fluid similar to sea water and any slight loss of fluid in the system is compensated by sea water intake through the madreporite . beating of the cilia of the ambulacral system facilitates the entry of water into the system. This fluid moves through stone canal, ring canal, radial canals, lateral canals and finally reaches the ampullae of the tube feet. During movement the tube feet perform a sort of stepping action

11. Food Capture: While feeding, the tube feet are used to hold the prey and also to open the shells of molluscs . Attachment: The suckers of the tube feet help the animal to remain anchored to rocks and other hard substrata. Respiration, Excretion and Sensation: In many echinoderms, the tube feet are not locomotory in function. Instead, they become modified to serve as respiratory, sensory and excretory structures ( eg . sea cucumber, sea lily, etc.).