Q.87 Which ONE of the following animals has “Osculum” as an excretory structure?
(A) Hydra (B) Sponge (C) Jelly Fish (D) Sea pen
Osculum excretory structure mcq questions test phylum-specific anatomy in NEET, UPSC, and GATE exams. Q.87 asks which animal uses osculum for excretion among Hydra, Sponge, Jellyfish, and Sea Pen. The correct answer is (B) Sponge.
✅ Correct Answer: (B) Sponge
Osculum = Large opening in sponges (Phylum Porifera) through which water exits carrying waste.
Water flow: Ostia (small pores) → Spongocoel → Osculum (exits with wastes).
Key features:
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Sponges lack true tissues/organs
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Excrete via diffusion into water current
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Osculum = excretory + respiratory + feeding outlet
❌ Why Other Options Are Wrong
| Option | Animal | Phylum | Excretory System | Why NOT Osculum |
|---|---|---|---|---|
| (A) | Hydra | Cnidaria | Diffusion through body surface | No osculum; simple sac-like gut |
| (B) | Sponge | Porifera | Osculum (water current) | ✅ CORRECT |
| (C) | Jelly Fish | Cnidaria | Diffusion + gastrovascular cavity | No osculum; medusa/polyp form |
| (D) | Sea pen | Cnidaria (Anthozoa) | Diffusion through tissues | Colonial coral-like; no osculum |
Phylum-Wise Excretory Structures Quick Guide
Porifera (Sponge) → Osculum ✅
Ostia → Choanocytes → Spongocoel → OSCULUM (exits)
Cnidaria (Hydra/Jelly/Sea pen) → No specialized organs
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Waste diffuses directly through body surface
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No osculum, nephridia, or Malpighian tubules
Exam Memory Trick: “OSCULUM = Only Sponge’s Cleanup Large Unique Mouth”
Pattern recognition:
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Porifera questions always mention osculum/ostia
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Cnidaria questions mention cnidoblasts/tentacles/gastrovascular cavity
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3 Cnidarians + 1 Poriferan = Pick the sponge!
Visual Identification for Exams
SPONGE: Other Animals:
_____ No osculum!
/ \
|Ostia | → Hydra: Mouth/anus
\_____/ Jelly: Diffusion
\|/ Sea pen: Diffusion
OSCULUM 💧
Master osculum excretory structure mcq – this exact pattern repeats in NEET/GATE!
One-word answer: SPONGE (B) – Only Porifera has osculum as excretory structure among given options.
