📘 Phylum Echinodermata – Spiny-Skinned Marine Animals

🔹 General Features:

• Exclusively marine animals with various shapes:

• 🌟 Star-shaped (e.g., sea star, brittle star)
• 🍩 Flattened (e.g., cake urchin)
• ⚪ Globular (e.g., sea urchin)
• 🥒 Elongated (e.g., sea cucumber)

🔹 Body Structure:

• Triploblastic, deuterostome coelomates
• Larvae: Bilateral symmetry
• Adults: Radial symmetry (pentaradial – in 5s or multiples)
• Endoskeleton made of calcareous ossicles with spines (from mesoderm + skin)

🔹 Water Vascular System:

• Unique system of canals for movement & feeding

• Main parts:

• Madreporite → ring canal → radial canals → lateral canals → tube feet
• Tube feet allow attachment to surfaces and movement via suction

🔹 Digestive & Nervous System:

• Complete tube-like digestive tract
• Nervous system: Nerve net + nerve ring + radial nerves
• Sensory cells on skin and tube feet

🔹 Respiration & Excretion:

• No specialized organs for respiration or excretion

🔹 Reproduction:

• Unisexual
• Asexual reproduction via body division and regeneration
• Capable of autotomy (dropping body parts under threat)

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✅ Examples of Echinoderms:

• Sea star, brittle star, sea urchin, cake urchin, sea cucumber

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