In this post we will certainly discuss around Water Vascular system of Echinoderms:- 1. Advent to Water Vascular device 2. Contents the Water Vascular mechanism 3. General setup 4. Changes 5. Functions.

Introduction to Water Vascular System:

The water vascular mechanism is enterocoelic in ori­gin and arises native the left hydrocoel. The exhibits radial symmetry indigenous the beginning and also is equally emerged in all Echinoderms.

This device lies just above the haemal sys­tem. It is primarily locomotory in duty and also sub-serves the duty of tactile and also respiratory organs in some cases. The excre­tory duty of water vascular system, said by some workers, is no yet fully ascertained.




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Histological picture reveals the the ca­nals have an within lining of flat ciliated epithelium, a great of longitudinal muscles, a connective organization layer and an outermost great of flat ciliated cells.

Contents the Water Vascular System:

The canals the the water vascular device contain a fluid of albuminous nature. The con­tains sea water and also leucocytes. Presence of red corpuscles is taped in one Ophiuroid, Ophiactis virens. Binyon (1964) has shown that the level the potassium in the liquid may be as lot as 60% over the sea water value. Boolootian (1966) has actually recognised 14 different types of amoebocytes in this fluid.

General plan of Water Vascular System:

The water vascular mechanism in different classes that Echinodermata has nearly the same structural organisation. It comprises of a couple of canals together with some appendages enclosed to these canals. The typical arrange­ment of the water vascular system is exhib­ited by Asterias.

The water vascular system has a circumoral canal (circular ambulacral or ring canal) situated about the mouth which gives tubular radial extensions, referred to as radial canals. The number of the radial canals is commonly five. Yet the number corre­sponds come the variety of the radii that the body.


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Each radial canal ends thoughtlessly at the finish of the arm and also gives off follow me its food lateral vessels, each joining a tube-foot. Every tube- foot is a hole conical or cylindrical procedure with an ampulla and also a terminal sucker. The junction in between the lateral vessels and the tube-feet is noted with valves which assist in locomotion.

The contraction of the ampul­lae results in the extension of the tube-feet. A short, slightly curved, cylindrical and verti­cally disposed stone or sand canal is present between the madreporite and the ring canal. The stone canal opens right into the ring canal in ~ the dental end and into the madreporic ampulla in ~ the aboral end.

The madreporite is a skel­etal plate-like structure placed at the aboral side. It is perforated through pores, called the madreporic pores, i m sorry lead right into madreporic ampulla or vesicle from wherein the rock canal starts. The stone canal is surrounding by a wider canal, referred to as axial sinus, the wall surface of which i do not care folded to form the axial body organ or dorsal body organ or ovoid gland or heart. The duty of axial body organ is not fully known.

Besides the key vessels, part append­ages become associated with the system. Inter-radially located and connected v the ring canal, there space polian vesicles and Tiedemann’s bodies. The Polian vesicles are bladder-like sacs with narrower neck.

They space contractile and also usually manufac­ture amoeboid cells. The Tiedemann’s bod­ies space glandular in nature and also consist that a variety of branched tubules. They space yel­lowish in colour and also give origin to cells because that the water vascular system.

Modifications the the Water Vascular mechanism in various Classes:

The water vascular system is equally emerged in every Echinoderms and also has basi­cally the same structural plan. In the differ­ent classes, slim deviations native the simple plan are encountered. The variations are due to their adaptations to various modes of living.

Madreporite:

In Asteroidea (Fig. 21.7B), that is a calcareous sieve-like plate and also is situ­ated aborally. The boost in variety of the madreporite is it was observed in many Asteroidea. The variety of madreporites is 3 in Asterias capensis, 4 in A, tenuispina, 16 in Acanthaster echinites. The madreporite is noted with many an additional water-pores. Many of the water-pores command into rock canal and also rest right into the axial sinus in adults.

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The water-pores are numerous in number and also develop indigenous one primary larval water-pore. Prefer Asteroidea, in Echinoidea (Fig. 21.16) also the madreporite possesses countless pores, but Echinocyamus pusillus, is peculiar in having actually only one water-pore. In Ophiuroidea, the madreporite has actually one water-pore, but in Ophiurae and Astrophytidae there are sev­eral water pores.

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In Holothuroidea true madreporite is absent. Good variations space observed regard­ing the opening of the stone canal. In Pelagothuria it opens up to the exterior through one pore and also in numerous Elasipodidae there are 2 come 50 or much more pores. However in part Elasipodidae and also Molpadidae the stone canal opens right into the coelom by numerous pores rather of open­ing to the exterior.

In the rest of the Holothurians, the rock canal opens into the axial sinus which consequently opens to the exte­rior by one or much more water-pores i m sorry are similar to madreporite. The madreporite in this situation may finest be called as internal madreporite.

In Crinoidea, madreporite is represented by good water-pores top top the human body surface and also these water-pores lead directly into the human body cavity. The water-pores are videotaped to it is in 1500 in Antedon bifidia.


Stone canal:

Normally the stone canal is a short, slightly curved and vertically dis­posed cylindrical tube. That opens into the ring canal in ~ the oral end. The is fastened by the wall of another vast canal, the axial sinus.

In Asteroidea, the rock canal is one and ‘S’-shaped. Yet in Asterias rubens, there are two rock canals. The wall of the rock canal is listed with calcareous ossicles. Devel­opment that a longitudinal ridge-like projec­tion makes the stone canal complex in the different members of the Asteroidea (Fig. 21.37).

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The following problems are encoun­tered:


(1) In Echinaster purpureus, the fold projects as a ridge into the canal. This repre­sents the simplest condition.

(2) In Asterina gibbosa, the totally free terminal finish divides right into two lamellae which might be coiled. This is watched in Asterias and Gymnasterias.

(3) In Astropecten, the coiled lamellae become very complicated and extend in between the walls from one next to another of the lumen.


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

In Echinoidea, the rock canal is only one and has soft membranous wall devoid that calcareous matter. In Cedaris, the wall of the rock canal is listed with calcareous deposit. The stone canal has an ampulla below the madreporite.

In Ophiuroidea, the rock canal is devoid of calcareous deposition and also opens in among the oral plates (Sedjwick, 1898). In Trichaster elegans, there room five stone canals. In Ophiactis virens, the rock canals are many.

In Holothuroidea, the rock canal is mostly single but in some cases it may be much more than one. The number of accessory stone canal is also variable. Its walls are provided with calcareous matters.

The open­ing that the rock canal shows best varia­tion, particularly in Holothurians. The stone canals in all Holothurians room attached to human body wall. In Pelagothuria, the stone canal opens up to the exterior by one or numerous pores. This likewise is true in many Elasipodidae.

In your one, the rock canal is branched. In some Elasipodidae and also Molpadidae the stone ca­nal ends blindly and opens internally right into the coelom by numerous pores together in the genus Elasipoda.




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In Crinoidea, rock canal because of this is ab­sent. Many tubes, without calcareous deposits in your walls, arising from the ring vessel space the to represent of the stone canals of various other groups.

Axial sinus and also axial organ:

The axial sinus is variously emerged in different Echinoderms. The is quite unique from the perivisceral cavity in adult excepting some Holothurians and Crinoids. The axial sinus is inconspicuous in Asteroids, very tiny in Echinoids and also Ophiuroids. The axial organ, a fold from the wall surface of the axial sinus, is current in every Echinoderms excepting Holothurians.

The axial organ comprises connective tissue and also cells that germinal rudi­ment. In Echinoids the axial sinus ends blindly and communicates through the stone canal. In Crinoids, the section of the coelom, into which the tubes indigenous the ring vessel open, to represent the axial sinus. The axial organ occupies the axis of the body. It con­sists the anastomosing canals installed in connective tissue.

Ring canal and Radial canals. The ring canal is a constant structure in every Echinoderms and also is positioned round the mouth. It provides tubular prolongations along the radii, referred to as radial canals or radial ves­sels. In Asteroidea, the ring canal is pen­tagonal and is positioned in the buccal mem­brane (peristome). That is connected with the exterior v the rock canal and axial sinus.

In Echinoidea, the ring canal is situ­ated in ~ the upper end of the jaws and gives five radial vessels. In Ophiuroidea, the con­dition is same as in Asteroidea. In Holothuroidea, the ring canal is situated approximately the oesophagus and the 5 raidal vessels extend towards the oral end and also again continue aborally along the radii of the body.


The radial vessels end blindly and also the terminal tentacle, characteristics of Asteroidea and Echinoidea, is absent. The number of radial vessels room five. Castle are lacking in Synaptidae. In situation of Crinoidea, the termi­nal tentacles are missing and the radial vessels finish blindly.

Lateral vessels and Tube-feet:

The radial vessels provide lateral vessels to the tube-feet. The tube-feet room cylindrical processes and their cavities are constant with the water vascular system. The tube-feet possess am­pullae at your inner ends and also suckers in ~ the terminal ends. The ampullae are existing in every echinoderms, other than Ophiuroidea and Crinoidea.

In Crinoidea, terminal suckers are lacking and the tube-feet space sensory and respiratory in function. In many Astropectinidae, each tube-foot is listed with 2 ampullae. In every the members that the Asteroidea the tube-feet are listed with well-developed suctorial disc-like expan­sions.

In Echinoidea, the tube-feet present varia­tions. In Endocyclica, the terminal ends of the tube-feet room suctorial and supported through calcareous rings. In Cidaridae and Echinothuridae, little oral tube-feet project from the perforations the the ambulacral bowl which space olfactory in nature. In Clypeasteroids, the tube-feet are wide and the walls are devoid the calcareous bodies. They assist in respiration.

The cylindrical tube- feet which are suctorial and detailed with calcareous rings, space locomotory in function. However in Spatangoids, the tube-feet vary quite significantly which are due to their functional activities.

The tube-feet there is no suckers space respiratory in function; v suckers and also calcareous ring are locomotory in function; with increased terminal disc and also filaments roughly the mouth as the tactile organ; ro­sette feet act together prehensile organs and seize food from the surroundings.

In Ophiuroidea, the orientation the the lateral vessels and the tube-feet is exact same as in Asteroidea, yet they are devoid the ampullae and are solely sensory in function.

In Holothuroidea, lateral branches indigenous the radial vessels get in the tube-feet and also into the tentacles. Some lateral branches also emerge from the radial vessels and end thoughtlessly in the body wall. Ampullae are existing in the tube-feet and also in the tentacular canals. The tentacular canals are devoid that ampullae in Elasipodidae wherein they arise straight from the ring canal.

Among the Crinoidea, in Antedon, each lateral branch indigenous the radial vessel gives three tube-feet. The tube-feet have actually ampullae. They space purely respiratory and also sensory in function.

Polian Vesicle and also Tiedemann’s Bodies:

The ring canal possesses bladder-like polian vesicles and also gland-like Tiedemann’s bodies. In Asteroidea, the variety of polian vesicles varies greatly. Lock are totally ab­sent in Asterias rubens and A. Glacialis. Over there are situations where 2 or numerous polian vesicles might be existing in each inter-radius as viewed in Astropecten.

In this case, a couple of vesicles open right into the ring canal through one common stalk (Fig. 21.38). The Tiedemann’s bodies room attached come the ring canal and are usually 2 in every inter-radius excepting that con­taining the madreporite where just one is present.

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Amongst Echinoidea, in many Endocylica, a little spongy outgrowth in every inter-radius is present which is sup­posed to be the polian vesicle. There are 5 Tiedemann’s bodies in Echinoidea. In Ophiuroidea, in each inter-radius excepting the of rock canal, there is a polian vesicle.

In Ophiactis virens, besides two or three polian vesicles opened in each inter-radius, there are numerous tubular canal the Simroth (sup­posed come be respiratory tract in function). The Tiedmann’s bodies appear to it is in wanting. Some authorities express some structures ho­mologous with Tiedmann’s bodies.

Some say that the radiant protrusions are discovered in part places. Hyman (1955) likewise refers the these space Tiedmann’s bodies. Fedetov (1926) has reported the the radial protrusion is associated with water ring in Ophiactum sericeum.

In Gorgonocephalus, a bunch the pouch-­like frameworks or branching tubules are current in water ring. The did not point out it together Tiedmann’s bodies yet represented it as spe­cialized structure.

Hyman (1955) said probably this structure discussed in these above ani­mals together homologous with the Tiedmann’s bodies. In Holothuroidea, commonly one big polian vesicle is present. In some impressive cases an ext than one polian vesicle may be present. In Crinoidea, the polian vesicle and Tiedemann’s bodies are absent.

Functions of the Water Vascular System:

1. Locomotion:

The main duty of the water vascular mechanism is to assist in locomotion. Echinoderms having suctorial podia (tube-feet) can adhere to the substratum temporarily. The mecha­nism the locomotion has questioned in detail under the water vascular device of Asterias and also Echinus.

2. Respiratory and also sensory:

In Ophiuroidea and also Holothuridea the tube-feet (podia) are mainly sensory in function. In Echinoidea (in continuous urchins), the tube-feet the the aboral side absence terminal disc and are sensory in duty (Hyman, 1955).

In spatangoids, the petaloids the the abo­ral surface ar are noted with lobulated po­dia without suckers and also are thought to part respiratory in function (Loven, 1883).

3. Excretory:

Nitrogenous wastes are got rid of through the thin areas of the body surface ar such together the walls of tube-feet.