Water vascular system (or) Ambulacral system is a peculiar system which is seen in only Echinoderms. This system is modified in different ways in the members belonging to different classes of phylum echinodermata.
The water vascular system in Asteroidea is considered as typical system.
1. Water vascular system in Asteroidea:
2. Water vascular system in Echinoidea:
Water vascular system of Echinoidea will resemble the typical water vascular system of Star fish.
- On the aboral side Madreporite is present.
- Madreporite is connected to ring canal by 'S shaped stone canal.
- Around the pharynx ring canal is present. It is placed above the aristotle lantren.
- From ring canal 5 radial canals will arise. They end as tentacles at the end of each arm.
- From radial canals lateral canals will arise. These lateral canals will end as tube feet.
- Each tube foot shows ampulla, podium and sucker.
- At the five inter radii of the ring canal five polian vesicles are present. They produce amoebpcytes.
- Tiedmann's bodies are absent.
3. Water vascular system in Holothuroidea:
The members of this class are called sea-cucumbers.
- Madreporite hangs into the body cavity.
- From madreporite stone canal will reach the ring canal. One or many ring canals may be present.
- The ring canal is present around the oesophagus.
- From ring canal 5 radial canals will arise. They travel to the oral region give branches to tentacles. Then they travel aborally.
- From each radial canal lateral canals will arise.
- Each lateral canal will end with tube foot.
- Tube foot has no sucker.
- From ring canal 10 to 50 polian vesicles will hang into the body cavity.
4. Water vascular system in Crinoidea:
This class includes sea lilies. They are sedentary animals.
- Madreporite is absent.
- Ring canal is present around mouth.
- From ring canal 5 radial canals will arise. Each radial canal will divide into two. Thus 10 radial canals will travel into 10 arms.
- From radial canals lateral canals will arise.
- Each lateral canal gives tube foot.
- Tube foot will not show ampulla and sucker. Hence they are useful as tactile sense organs and for respiration.
5. Water vascular system in Ophuroidea:
Brittle stars are included in this class.
- Madreporite is present on the oral surface.
- Stone canal will connect madreporite vctth ring canal.
- Ring canal is present around the mouth.
- From ring canal 5 radial canals will arise.
- Each radial canal will give lateral canals.
- Each lateral canal ends in tube foot.
- Tube foot has no ampulla and sucker. Hence they are useful for respiration and work as tactile sense organs.
- At the 4 inter radii 4 polian vesicles are present. Tiedmann bodies are absent.
Thus water vascular system is modified in different classes of Echinodermata.