WATER VASCULAR SYSTEM THAT CHARACTERIZES ANIMALS THAT OCCURS IN THE PHYLUM ECHINODERMATA.

Animal that belonging to the phylum echinodermata has water vascular, which is consist of radial canals. Madreporite is the water vascular system opening, which lies on interambulacrum. The water vascular system performs many important functions such as locomotion, respiration, and feeding in echinoderms. “This phylum is characterised by radial symmetry, several arm and the body actually consists of five equal segments, each containing a duplicate set of various internal organs. They have no heart, brain, and eyes; but some like brittle stars have light sensitive parts on their arms. Their mouth is situated on the underside and their anus on top except feather stars, sea cucumber and urchins. Vascular system supplies water through canals of small muscular tubes to the tube feet” (1)

There are five classes of Phylum echinoderms namely: class asteroidea, e.g. Starfish or sea stars. Species belonging to the class asteroidea have madreporite on aboral surface and water vascular system is connected by ampulla under madreporite. Ampulla is then connected to stone canal and ring canal. Ring canal is connected to lateral canals that pass through pores in the skeletal plates and end in tube feet. Tube feet move by combination of muscles and hydraulics. Tube feet from the water vascular system in asteroids help in locomotion. Class Crinoidea, e.g. Feather star, have a long stalk with branching arms that attach them to rocks and the ocean bottom and can move around.

Class Ophiuroidea: The water vascular system in species belonging to the class ophiuroidea has a much smaller central disc and no anus. They remove waste in the form of mouth which is situated on the base centre. “On the other side of the body disk there is a splitlike opening at the base of each side of each arm. These ten opening are breathing and reproductive outlets, taking in water for oxygen and sheeding eggs or sperm into the sea” (1)

Class Echinoidea: e.g. include sea urchins and sand dollars. The mouth consists of a complex arrangement of muscles and plates surrounding the circular opening. The anus is located on the upper surface and some sea urchins have a spherical, bulb like cloaca (to store fecal material) that protudes from the anal opening (2).

In conclusion: The water vascular system in species belonging to the phylum echinodermata is responsible for locomotion, respiration and feeding.

References:

1) Deutsch. Invertebrates, multi-celled animals (Metazoa) [Internet]. Online access: 2006 May 04,14:34 [cited 2006 May 05].Available from: http://www.starfish.ch/reef/echinoderms.html
2) Tree of life web project. Wray .A.G, Echinodermata [Internet]. Online access: 2006 May 05, 15:08 [cited 2006 May 05].Available from:
http://tolweb.org/Echinodermata

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