1. Pinacocytes:
* Function: These flat, thin cells form the outer layer of the sponge, known as the pinacoderm. They act like a protective "skin," providing structural support and regulating the passage of water into the sponge's internal cavities.
2. Choanocytes (Collar Cells):
* Function: Found lining the internal chambers (spongocoel and canals) of the sponge. They have a flagellum (whip-like tail) and a collar of microvilli (tiny projections) surrounding the base of the flagellum.
* Flagellar movement: The flagella beat rhythmically, creating a current that draws water into the sponge.
* Food capture: The collar traps food particles (bacteria, algae, etc.) from the water.
3. Archaeocytes:
* Function: Amoeboid cells (meaning they can move) that are found throughout the sponge mesohyl (the jelly-like layer between the pinacoderm and choanoderm). They are multi-functional:
* Phagocytosis: They engulf and digest food particles.
* Totipotency: They can differentiate into other sponge cell types, like sclerocytes and spongocytes.
* Storage: They store food reserves.
* Repair and regeneration: They play a role in repairing damage and regenerating lost parts of the sponge.
4. Sclerocytes:
* Function: These cells secrete the skeletal elements of the sponge, called spicules. Spicules are made of calcium carbonate (calcareous sponges) or silica (glass sponges), providing structural support and protection.
5. Spongocytes:
* Function: Spongocytes produce the protein fibers known as spongin. Spongin adds flexibility and support to the sponge's skeleton.
6. Porocytes:
* Function: These cells form the pores (ostia) through which water enters the sponge. They are essentially tube-shaped cells that connect the outside environment to the sponge's internal canals.
Additional Notes:
* Mesohyl: The jelly-like layer between the pinacoderm and choanoderm. It contains archaeocytes and other cell types, as well as skeletal elements.
* Spongocoel: The central cavity of the sponge.
Let me know if you'd like more details on any of these cell types or their functions!
