Cell Types
Organisms of the Phylum Porifera have pinacocytes, mesenchyme cells, and choanocytes.
Pinacocytes are thin flat cells that line the outer surface of a sponge. These cells can contract, which can change the shape of some sponges. There are specialized pinacocytes called porocytes. Porocytes regulate water circulation, this is done by acting as pathways for water to travel through the sponge wall.
Mesenchyme cells move freely in the mesohyl (jelly like layer below pinacocytes) and are useful in reproduction, secreting skeletal elements, transporting and storing food, and forming contractile rings around openings in the sponge wall.
Choanocytes lay under the mesohyl, they also line the inner chamber(s) of the sponge. These cells are flagellated and they posses a collar-like ring of microvilli that surrounds a flagellum. The fact that sponges have choanocytes can explain that choanoflagellates, a group of protists, are related.
Mesenchyme cells move freely in the mesohyl (jelly like layer below pinacocytes) and are useful in reproduction, secreting skeletal elements, transporting and storing food, and forming contractile rings around openings in the sponge wall.
Choanocytes lay under the mesohyl, they also line the inner chamber(s) of the sponge. These cells are flagellated and they posses a collar-like ring of microvilli that surrounds a flagellum. The fact that sponges have choanocytes can explain that choanoflagellates, a group of protists, are related.