Question

Osculum is lined by-
A. Myocytes cells
B. Pinacocyte cells
C. Collar cells
D. None of the above.

Answer 1

Hint: Phylum Porifera includes the members commonly known as sponges and are generally marine. They are primitive, multicellular, asymmetrical in geometry, and have a cellular level of organization in body. They have a water transport system or canal system present in them. The osculum is an excretory structure present in the sponges.

Complete answer:
Myocytes or the muscle cells, further conduct signals and cause parts of the sponges to contract. Such contractions are entirely responsible for the closing of the osculum and then transmitting signals between the different parts of the body. A spongocoel is known to be the large, central cavity found in sponges. Water here enters the spongocoel through hundreds of minute pores known as Ostia and exits out through the further larger opening known as osculum. Depending on the body plan of the sponge (which can either be asconoid, syconoid, or leuconoid), the spongocoel could be marked as a simple interior space of the sponge or sometimes a complexly branched inner structure. In Spite of the body plan or class they belong to, the spongocoel is lined with choanocytes cells, which have flagella that push water through the spongocoel, further creating a water current.

So, the correct option is option A i.e. myocyte cells.

Note:
Though sponges do not exhibit tissue level of organization, still they do have different cell types that perform very different functions. Pinacocytes, which are epithelial cells, form the outermost layer of the sponges. Choanocytes or the collar cells are present at various locations, depending on the type or class of sponges, Whereas pinacocytes line the outside of the sponge, and choanocytes tend to line certain inner portions of the sponge body that surround the mesohyl which is matrix.