The correct answer is (D) Echinodermata.​

This phylum features a unique water vascular system, a network of fluid-filled canals aiding locomotion, respiration, and feeding in marine animals like starfish and sea urchins. Other options lack this system entirely.​

Option Analysis

(A) Cnidaria

Cnidarians, such as jellyfish and corals, exhibit radial symmetry and use a gastrovascular cavity for digestion and gas exchange, but possess no water vascular system or tube feet.​

(B) Annelida

Annelids, like earthworms and leeches, feature a closed circulatory system with dorsal and ventral blood vessels, metameric segmentation, and parapodia in some, without any water vascular system.​

(C) Mollusca

Molluscs, including snails and octopuses, have an open circulatory system (closed in cephalopods), a muscular foot for movement, and gills or lungs, but no water vascular system.​

(D) Echinodermata

Echinoderms are defined by their pentaradial symmetry, spiny endoskeleton, and water vascular system—a hydraulic network with a madreporite, stone canal, ring canal, radial canals, and tube feet for key functions.​

The phylum with water vascular system is Echinodermata, a group of exclusively marine deuterostomes featuring this unique hydraulic structure for locomotion and more. Ideal for CSIR NET Life Sciences aspirants, understanding this distinction clarifies animal kingdom classifications.​

Water Vascular System Functions

This system circulates seawater via canals connected to tube feet, enabling:

• Locomotion through hydraulic pressure in tube feet.​

• Food capture and transport in starfish.​

• Respiration and excretion via diffusion.​

Components include the madreporite (water entry), stone canal, ring canal, and radial canals branching into arms.​

Why Only Echinodermata?

Unlike Cnidaria’s gastrovascular cavity, Annelida’s blood vessels, or Mollusca’s hemocoel, Echinodermata’s system derives from the coelom, supporting radial symmetry and regeneration. No other phylum shares this trait.​

Exam Relevance

Common in CSIR NET MCQs, this identifies Echinodermata over distractors like Mollusca. Examples: starfish (Asterias), sea urchins (Echinus).​