In echinoderms such as sea stars, locomotion and food capture rely on a hydraulic water vascular system. Arrange the following structural stages in the correct sequential order of fluid movement, starting from seawater intake to tube foot extension. Which order accurately traces this hydraulic pathway?
- 1Seawater enters through the perforated madreporite on the aboral surface
- 2Fluid passes down the rigid, calcified stone canal
- 3Water enters the circular ring canal surrounding the central gut
- 4Fluid diverges into radial canals extending along the ambulacral groove of each arm
- 5Muscular ampullae contract, forcing water into the podium of each tube foot
Answer
The correct sequence starts with intake at the madreporite, proceeds through the stone canal into the ring canal, branches along the radial canals, and ends with fluid propulsion from the ampullae into the tube feet.
The correct order follows the unidirectional hydraulic flow of seawater in echinoderms: Intake occurs at the madreporite, travels down the stone canal to the central ring canal, disperses along the radial canals of each arm, and culminates in ampullary contraction forcing fluid into the tube feet.
Step-by-Step Solution
Key Concept
Echinoderm Water Vascular System Flow Pathway