In this short article we will certainly talk about around Water Vascular System of Echinoderms:- 1. Review to Water Vascular System 2. Materials of Water Vascular System 3. General Plan 4. Modifications 5. Functions.

Review to Water Vascular System:

The water vascular mechanism is enterocoelic in ori­gin and arises from the left hydrocoel. It exhibits radial symmeattempt from the start and is equally developed in all Echinoderms.

This mechanism lies simply over the haemal sys­tem. It is mainly locomotory in feature and likewise sub-serves the feature of tactile and respiratory organs in some situations. The excre­tory function of water vascular device, suggested by some employees, is not yet totally ascertained.

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Histological image reveals that the ca­nals have an inner lining of level ciliated epithelium, a layer of longitudinal muscles, a connective tissue layer and also an outermost layer of level ciliated cells.

Components of Water Vascular System:

The canals of the water vascular system contain a fluid of albuminous nature. It con­tains sea water and also leucocytes. Existence of red corpuscles is tape-recorded in an Ophiuroid, Ophiactis virens. Binyon (1964) has actually displayed that the level of potassium in the fluid may be as much as 60% above the sea water worth. Boolootian (1966) has recognised 14 different forms of amoebocytes in this liquid.

General Plan of Water Vascular System:

The water vascular mechanism in various classes of Echinodermata has almost the exact same structural organisation. It comprises of a couple of canals in addition to some appenderas attached to these canals. The typical arrange­ment of the water vascular mechanism is exhib­ited by Asterias.

The water vascular device includes a circumoral canal (circular ambulacral or ring canal) located roughly the mouth which offers tubular radial extensions, dubbed radial canals. The number of the radial canals is generally 5. But the number corre­sponds to the variety of the radii of the body.


Each radial canal ends thoughtlessly at the end of the arm and also provides off along its course lateral vessels, each joining a tube-foot. Each tube- foot is a hollow conical or cylindrical process via an ampulla and also a terminal sucker. The junction between the lateral vessels and the tube-feet is gave through valves which assist in locomovement.

The contractivity of the ampul­lae outcomes in the extension of the tube-feet. A short, slightly curved, cylindrical and also verti­cally disposed stone or sand also canal is existing in between the madreporite and also the ring canal. The stone canal opens up right into the ring canal at the dental end and also into the madreporic ampulla at the abdental end.

The madreporite is a skel­etal plate-like structure put at the abdental side. It is perforated by pores, called the madreporic pores, which lead into madreporic ampulla or vesicle from wright here the rock canal starts. The rock canal is surrounded by a more comprehensive canal, called axial sinus, the wall of which becomes folded to form the axial organ or dorsal organ or ovoid gland or heart. The function of axial organ is not fully known.

Besides the main vessels, some append­ages come to be linked through the system. Inter-radially located and also associated through the ring canal, tbelow are polian vesicles and Tiedemann’s bodies. The Polian vesicles are bladder-choose sacs via narrower neck.

They are contractile and also generally manufac­ture amoeboid cells. The Tiedemann’s bod­ies are glandular in nature and consist of a number of branched tubules. They are yel­lowish in colour and give beginning to cells for the water vascular device.

Modifications of the Water Vascular System in Different Classes:

The water vascular mechanism is equally occurred in all Echinoderms and has actually basi­cally the very same structural plan. In the differ­ent classes, slight deviations from the standard setup are encountered. The variations are due to their adaptations to various settings of living.


In Asteroconcept (Fig. 21.7B), it is a calcareous sieve-prefer plate and is situ­ated aborally. The boost in number of the madreporite is observed in many type of Asteroidea. The number of madreporites is 3 in Asterias capensis, 4 in A, tenuispina, 16 in Acanthaster echinites. The madreporite is provided with many kind of second water-pores. Many of the water-pores lead right into stone canal and rest right into the axial sinus in adults.


The water-pores are many in number and construct from one major larval water-pore. Like Asteroprinciple, in Echinoprinciple (Fig. 21.16) likewise the madreporite possesses many pores, yet Echinocyamus pusillus, is strange in having just one water-pore. In Ophiuroprinciple, the madreporite has actually one water-pore, yet in Ophiurae and also Astrophytidae tbelow are sev­eral water pores.


In Holothuroidea true madreporite is lacking. Great variations are observed regard­ing the opening of the stone canal. In Pelagothuria it opens to the exterior by one pore and also in many Elasipodidae there are 2 to 50 or even more pores. But in some Elasipodidae and also Molpadidae the stone canal opens up into the coelom by many pores rather of open­ing to the exterior.

In the remainder of the Holothurians, the stone canal opens right into the axial sinus which consequently opens to the exte­rior by one or more water-pores which are similar to madreporite. The madreporite in this case may best be referred to as as internal madreporite.

In Crinoprinciple, madreporite is represented by fine water-pores on the body surface and these water-pores lead straight into the body cavity. The water-pores are videotaped to be 1500 in Antedon bifidia.

Stone canal:

Typically the rock canal is a brief, slightly curved and vertically dis­posed cylindrical tube. It opens up right into the ring canal at the dental finish. It is enclosed by the wall of one more wide canal, the axial sinus.

In Asteroconcept, the stone canal is one and ‘S’-shaped. But in Asterias rubens, tbelow are 2 rock canals. The wall of the rock canal is offered with calcareous ossicles. Devel­opment of a longitudinal ridge-prefer projec­tion provides the rock canal complicated in the various members of the Asteroconcept (Fig. 21.37).


The adhering to conditions are encoun­tered:

(1) In Echinaster purpureus, the fold jobs as a ridge right into the canal. This repre­sents the simplest problem.

(2) In Asterina gibbosa, the complimentary terminal end divides into 2 lamellae which may be coiled. This is viewed in Asterias and Gymnasterias.

(3) In Astropecten, the coiled lamellae end up being very complex and also extfinish in between the wall surfaces from one side to one more of the lumen.

(4) In Culcita and Astropecten aurantiacus, the entirety lumen becomes divided right into a variety of irconsistent chambers.

In Echinoconcept, the rock canal is only one and has actually soft membranous wall devoid of calcareous matter. In Cedaris, the wevery one of the rock canal is offered via calcareous deposit. The rock canal has actually an ampulla listed below the madreporite.

In Ophiuroconcept, the stone canal is devoid of calcareous deplace and opens up in among the oral plates (Sedjwick, 1898). In Trichaster elegans, tright here are five stone canals. In Ophiactis virens, the rock canals are many type of.

In Holothuroidea, the stone canal is mainly single yet in some situations it may be more than one. The number of accessory rock canal is additionally variable. Its walls are provided with calcareous matters.

The open­ing of the stone canal shows best varia­tion, particularly in Holothurians. The stone canals in all Holothurians are attached to body wall. In Pelagothuria, the rock canal opens to the exterior by one or many kind of pores. This also is true in many type of Elasipodidae.

In Thy one, the rock canal is branched. In some Elasipodidae and Molpadidae the stone ca­nal ends blindly and opens internally right into the coelom by many pores as in the genus Elasipoda.

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In Crinoidea, stone canal as such is ab­sent out. Several tubes, without calcareous deposits in their walls, arising from the ring vessel are the representatives of the rock canals of other groups.

Axial sinus and also axial organ:

The axial sinus is variously occurred in different Echinoderms. It is fairly unique from the perivisceral cavity in adult excepting some Holothurians and Crinoids. The axial sinus is inconspicuous in Asteroids, very little in Echinoids and also Ophiuroids. The axial body organ, a fold from the wall of the axial sinus, is existing in all Echinoderms excepting Holothurians.

The axial body organ comprises connective tproblem and cells of germinal rudi­ment. In Echinoids the axial sinus ends thoughtlessly and communicates via the rock canal. In Crinoids, the percent of the coelom, right into which the tubes from the ring vessel open up, represents the axial sinus. The axial organ occupies the axis of the body. It con­sists of anastomosing canals embedded in connective tproblem.

Ring canal and Radial canals. The ring canal is a continuous structure in all Echinoderms and is positioned round the mouth. It gives tubular prolongations alengthy the radii, called radial canals or radial ves­sels. In Asteroidea, the ring canal is pen­tagonal and is located in the buccal mem­brane (peristome). It is interacted through the exterior through the rock canal and axial sinus.

In Echinoprinciple, the ring canal is situ­ated at the top end of the jaws and also provides five radial vessels. In Ophiuroconcept, the con­dition is exact same as in Asteroprinciple. In Holothuroprinciple, the ring canal is situated roughly the oesophagus and also the 5 raidal vessels extend towards the oral finish and also again continue aborally alengthy the radii of the body.

The radial vessels end thoughtlessly and also the terminal tentacle, characteristic of Asteroprinciple and also Echinoconcept, is absent. The numbers of radial vessels are five. They are absent in Synaptidae. In case of Crinoconcept, the termi­nal tentacles are absent and also the radial vessels end blindly.

Lateral vessels and Tube-feet:

The radial vessels give lateral vessels to the tube-feet. The tube-feet are cylindrical procedures and their cavities are consistent through the water vascular device. The tube-feet possess am­pullae at their inner ends and also suckers at the terminal ends. The ampullae are present in all echinoderms, other than Ophiuroidea and also Crinoconcept.

In Crinoprinciple, terminal suckers are missing and also the tube-feet are sensory and also respiratory in attribute. In many Astropectinidae, each tube-foot is offered through two ampullae. In all the members of the Asteroconcept the tube-feet are offered via well-arisen suctorial disc-like expan­sions.

In Echinoconcept, the tube-feet display varia­tions. In Endocyclica, the terminal ends of the tube-feet are suctorial and sustained by calcareous rings. In Cidaridae and also Echinothuridae, little oral tube-feet project from the perforations of the ambulacral plates which are olmanufacturing facility in nature. In Clypeasteroids, the tube-feet are wide and also the wall surfaces are devoid of calcareous bodies. They aid in respiration.

The cylindrical tube- feet which are suctorial and offered through calcareous rings, are locomotory in function. But in Spatangoids, the tube-feet differ fairly significantly which are because of their sensible activities.

The tube-feet without suckers are respiratory in function; with suckers and calcareous ring are locomotory in function; through increased terminal disc and also filaments roughly the mouth as the tactile organ; ro­sette feet act as prehensile organs and seize food from the surroundings.

In Ophiuroprinciple, the orientation of the lateral vessels and also the tube-feet is very same as in Asteroidea, however they are devoid of ampullae and also are exclusively sensory in feature.

In Holothuroconcept, lateral branches from the radial vessels go right into the tube-feet and also right into the tentacles. Some lateral branches likewise emerge from the radial vessels and end thoughtlessly in the body wall. Ampullae are current in the tube-feet and also in the tentacular canals. The tentacular canals are devoid of ampullae in Elasipodidae where they arise straight from the ring canal.

Among the Crinoidea, in Antedon, each lateral branch from the radial vessel offers 3 tube-feet. The tube-feet have ampullae. They are pudepend respiratory and also sensory in function.

Polian Vesicle and also Tiedemann’s Bodies:

The ring canal possesses bladder-like polian vesicles and also gland-prefer Tiedemann’s bodies. In Asteroconcept, the number of polian vesicles varies substantially. They are totally ab­sent out in Asterias rubens and A. glacialis. There are situations wbelow two or many polian vesicles may be existing in each inter-radius as watched in Astropecten.

In this instance, a couple of vesicles open into the ring canal by one widespread stalk (Fig. 21.38). The Tiedemann’s bodies are attached to the ring canal and are commonly two in each inter-radius excepting that con­taining the madreporite wbelow only one is current.


Amongst Echinoconcept, in a lot of Endocylica, a little spongy outexpansion in each inter-radius is present which is sup­posed to be the polian vesicle. Tright here are 5 Tiedemann’s bodies in Echinoconcept. In Ophiuroconcept, in each inter-radius excepting that of stone canal, there is a polian vesicle.

In Ophiactis virens, besides 2 or 3 polian vesicles opening in each inter-radius, tright here are many kind of tubular canal of Simroth (sup­posed to be respiratory in function). The Tiedmann’s bodies show up to be wanting. Some authorities refer some structures ho­mologous via Tiedmann’s bodies.

Some say that the radiant protrusions are discovered in some locations. Hyguy (1955) additionally refers that these are Tiedmann’s bodies. Fedetov (1926) has actually reported that the radial protrusion is associated through water ring in Ophiactum sericeum.

In Gorgonocephalus, a bunch of pouch-­favor structures or branching tubules are present in water ring. He did not cite it as Tiedmann’s bodies but stood for it as spe­cialized structure.

Hyman (1955) sassist perhaps this framework discussed in these above ani­mals as homologous through the Tiedmann’s bodies. In Holothuroidea, commonly one large polian vesicle is present. In some outstanding cases more than one polian vesicle might be current. In Crinoconcept, the polian vesicle and Tiedemann’s bodies are missing.

Functions of the Water Vascular System:

1. Locomotion:

The major attribute of the water vascular system is to assist in locomovement. Echinoderms having suctorial podia (tube-feet) can adhere to the substratum temporarily. The mecha­nism of locomotion has actually discussed in detail under the water vascular system of Asterias and Echinus.

2. Respiratory and sensory:

In Ophiuroprinciple and Holothuridea the tube-feet (podia) are mainly sensory in attribute. In Echinoconcept (in continuous urchins), the tube-feet of the abdental side lack terminal disc and are sensory in attribute (Hyman, 1955).

In spatangoids, the petaloids of the abo­ral surconfront are offered with lobulated po­dia without suckers and are believed to some respiratory in feature (Lcooktop, 1883).

3. Excretory:

Nitrogenous wastes are removed with the thin areas of the body surchallenge such as the walls of tube-feet.