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Question

Difficulty: MediumHigher Invertebrates: Annelida, Mollusca, Arthropoda, and Echinodermata

Arrange the following anatomical structures of the water vascular system in an echinoderm (such as a starfish) in the correct sequential order of water flow during locomotion, starting from the point of entry.

  1. 1Madreporite
  2. 2Stone canal
  3. 3Ring canal
  4. 4Radial canal
  5. 5Ampullae and tube feet

Answer

The correct sequential path of water flow through the echinoderm water vascular system is: Madreporite → Stone canal → Ring canal → Radial canal → Ampullae and tube feet.
The water vascular system in echinoderms functions as a hydraulic apparatus for locomotion. Water enters through the sieve-like madreporite, passes down the stone canal to the central ring canal, moves outward into radial canals along each arm, and is finally squeezed by muscular ampullae to extend the tube feet.

Step-by-Step Solution

1
Identify the initial entry structure for water on the aboral surface of an echinoderm.
Seawater enters via the porous madreporite (sieve plate).
The madreporite serves as the intake filter regulating water entry into the system.
2
Trace the passage connecting the intake plate to the central ring.
Water flows down the calcareous stone canal.
The stone canal acts as a unyielding conduit leading fluid toward the central ring canal.
3
Follow the distribution from the central disc out into the radiating arms.
Water enters the circular ring canal surrounding the esophagus and diverges into five radial canals.
The ring canal distributes fluid evenly to each radial canal extending down each arm.
4
Determine the final effector structures that produce hydraulic pressure for movement.
Fluid enters the bulb-like ampullae, forcing water into the tube feet.
Contraction of muscular ampullae creates hydraulic pressure that extends the tube feet to grip surfaces.

Key Concept

Water Vascular System of Echinodermata
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Topics

Higher Invertebrates: Annelida, Mollusca, Arthropoda, and Echinodermata

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