PORIFERA

 

Porifera (Sponges) 

Porifera, commonly known as sponges, are the simplest multicellular animals. These aquatic invertebrates play a significant role in aquatic ecosystems by filtering water and providing habitat for various organisms.

🧬 Classification of Porifera

Porifera are classified into three major classes based on the type of skeleton and body structure:

  1. Class Calcarea – Calcareous sponges with calcium carbonate spicules.

  2. Class Hexactinellida – Glass sponges with six-rayed siliceous spicules.

  3. Class Demospongiae – The largest class, containing sponges with spongin fibers or silica-based spicules.

🌀 Canal System in Porifera

The canal system is the defining feature for water circulation and feeding:

  • Ascon Type – Simplest structure with a central cavity (spongocoel).

  • Sycon Type – Wall folded into canals for increased surface area.

  • Leucon Type – Highly complex with chambers and canals, found in most sponges.

🍽️ Feeding Mechanism

Sponges are filter feeders:

  • Water enters through pores (ostia), flows into the spongocoel, and exits through the osculum.

  • Specialized cells called choanocytes trap and digest food particles using flagella.

❌ Other Systems

Sponges lack many systems found in complex animals:

  • No nervous, digestive, circulatory, or respiratory systems.

  • All physiological processes occur through diffusion.

🌱 Reproduction in Porifera

Porifera exhibit both sexual and asexual reproduction:

  • Asexual: Through budding or fragmentation.

  • Sexual: Most are hermaphrodites. Fertilized eggs develop into free-swimming larvae.

🦴 Skeletal Structure

The skeleton provides support and protection:

  • Made of spongin fibers, spicules, or both.

  • Spongin – A form of collagen protein.

  • Spicules – Mineral elements that vary in shape and composition.

🔬 Types of Spicules

Spicules vary in shape and are used for classification:

  • Monaxon – Single-axis.

  • Triaxon – Three axes.

  • Polyaxon – Multiple radiating axes.

  • Can be made of silica or calcium carbonate.

porifera

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