The inner layer of a sponge, the mesohyl, contains several types of amoeboid cells, which secrete materials to form a skeleton-like structure for support. the exterior of a sponge is comprised of flattened cells that form an outer epithelium. Choanocytes are flagellated cells that line internal cavities and are responsible for pumping water and small particles into the sponge. Sponges are truly multicellular organisms. Sponge cells are unique because throughout their development they can differentiate from one type of cell to another
Explanation: There are about nine thousand species of sponges. Sponges have three types of cells which includes
1) Pinacocytes: They are thin walled and flat cells. They line the outer surface of a sponge. Pinacocytes are slightly contractile. The contraction may change the structure of some sponges. Most pinacocytes forms tube like contractile porocytes. Porocytes are responsible for water regulation.
2) Mesohyl: It is a jelly like layer present underneath the pinacocytes. Amoeboid cells are present in mesophyl. The Amoeboid cells are called mesenchyma cells. These cells are responsible for reproduction, secretion, skeletal elements, transporting and storing food and forming contractile rings around openings in the sponge wall.
3)Choanocytes: Also called collar cells are present below the mesohyl. They form the lining of the inner chamber. Choanocytes are flagellated cells. They have a collar like ring of microvilli surrounding a flagellum.The flagellum creates water currents through the sponge.
