Q.29 The structural basis in sponges is provided by which of the following?
(1) Pinacocytes
(2) Choanocytes
(3) Porocytes
(4) Amoebocytes
Sponge Body Structure Overview
Sponges (Phylum Porifera) lack true tissues but have specialized cells forming a porous body for filter-feeding. The structural basis refers to cells providing skeletal support and body framework, complemented by spicules or spongin fibers. Understanding these cells is essential for invertebrate zoology and exams like NEET.
Correct Answer: Structural Basis Provided by Pinacocytes (Option 1)
The correct answer is (1) Pinacocytes.
Pinacocytes form the outer epithelium (pinacoderm), covering the sponge’s surface and forming the body wall. They provide structural integrity, contract to regulate water flow, and secrete skeletal components. Pinacocytes create the basic framework, making them the structural basis.
Key role: Epidermal-like cells maintaining shape and enclosure.
Explanation of All Cell Types
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(1) Pinacocytes: Form outer layer and canals; provide structural support and contractility. Essential for body framework.
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(2) Choanocytes: Collar cells lining internal chambers (choanoderm). Beat flagella to create water currents for feeding; no structural role.
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(3) Porocytes: Tubular cells forming water canal pores (ostia/osculation). Regulate water entry/exit; specialized, not structural basis.
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(4) Amoebocytes (Archaeocytes): Wander freely; transport nutrients, form gametes, secrete spicules/spongin. Supportive but not primary structural cells.
| Cell Type | Location | Main Function | Structural Role? |
|---|---|---|---|
| Pinacocytes | Outer surface/canals | Epithelium, contraction | Yes (framework) |
| Choanocytes | Inner chambers | Flagellar feeding | No |
| Porocytes | Pores | Water regulation | No |
| Amoebocytes | Mesohyl | Transport, secretion | Partial |
Why Pinacocytes Matter in Sponges
Pinacocytes enable sponges’ simple body plan, working with mesohyl (gelatinous matrix) and skeleton for support. Unlike tissues in higher animals, this cellular specialization suits their sessile, aquatic lifestyle.
Explore sponge canal systems or spicule types in our Porifera series.
