Question

What is common in sponges having different types of canal system?
A) Apopyle
B) Paragastric cavity
C) Prosopyle
D) Radial Chambers

Answer 1

Hint: Body of all sponges is perforated by a large number of apertures through which water enters Inside body and flows through a system of criss-crossing canals collectively forming the canal system which is a characteristic feature of poriferans.

Complete answer:
1) Apopyle is a pore through which water passes out of a radial canal or flagellated chamber of a sponge.
2) From the word gastric we can estimate that paragastric is a cavity (hollow space) near the stomach opening out through cloaca. We have a kingdom Animalia which has some phylum. Some of them are Porifera, Nematoda, cnidaria etc. The respiratory process occurs through the general body surface. The sponges fall in the category which has the cavities for performing most of the work. As cnidaria perform only prey catching tasks by the cavity. It is common in all sponges no matter what the canal system is.
3) Prosopyle is a pore through which water is drawn from the outside into one of the saclike chambers formed by the evagination of the body wall. Its function is to bring water into contact with the choanocytes lining the spongocoel.
4) Radial chambers are formed by the out-pushing of the wall of an asconoid sponge at regular intervals into finger-like projections, called radial canals. At first these radial canals are free projections and the outside water surrounds their whole length, for there are no definite incurrent channels.

Thus, the correct answer is option B (Paragastric cavity).

Note:The paragastric cavity of sponges is lined by specialized cells called choanocytes.Trophocytes are present in the spongocoel and release digestive enzymes outside, causing the digestion of food in spongocoel.