Question

Passage from incurrent to radial canals is formed by
A. Choanocytes
B. Pinacocytes
C. Archaeocytes
D. Prosopyles

Answer 1

Hint: Sponge is an animal that belongs to the phylum Porifera and kingdom Animalia. These are multicellular organisms that are characterized by the presence of pores all over the body of the organism. They are commonly referred to as pore bearers. The radial canals present in the body of sponges allow the entry of water inside the body.

Complete answer: Choanocytes are commonly called as collar cells. Choanocytes form the inner lining of the radial canal. Choanocytes contain a flagellum for locomotion and are surrounded by microvilli. These collar cells or choanocytes form a type of cell layer called choanoderm inside the sponges. In asconoid sponges, they are seen as the dotting surface of the spongocoel. They form radial canals in syconoid sponges. A radial canal is present between the two incurrent canals. The ameboid cells found in sponges are called archaeocytes. The function of archaeocytes varies depending upon the species. They are totipotent cells which have the ability to differentiate and form into a whole new organ. The outer wall of the cavity of sponges is lined by flat cells called pinacocytes. These cells form the outermost layer of the sponge called Pinacoderm. The size and structure of the sponge are maintained by the slight contraction and expansion of the pinacocytes. They line the incurrent canals and the spongocoel of the sponge. The tubular cells of the sponge are called porocytes from the pores into the body of the sponge through the mesophyll. Porocytes form a passage called prosopyle from the incurrent canal to the radial canal. Thus, the water enters into the radial canal through the prosopyle from the incurrent canals.
So, option D is the correct option.

Note: The outer cover of a sponge called pinacoderm is made up of pinacocytes. It regulates the function of keeping the water out of the sponge body. In between the pinacocytes, tubular cells called porocyte is present which form the opening of pores called ostia. Porocytes regulate the function of allowing the water into the sponge body.