Question

Give a brief account on the canal system in sponges.

Answer 1

Hint: Sponges are the members of phylum Porifera which are multicellular organisms that have a full body of pores and channels which allow water to circulate through them. They consist of jelly like mesohyl which is sandwiched between two thin layers of the cells.

Complete answer:
Let us understand the canal system in sponges.
There are four types of canal systems that are found in sponges.
1.Ascon type, (with flagellated spongocoel)- It is the simplest type of canal system. In this the ostia is present on the surface of the body of sponges which lead to the spongocoel which is further lined up by choanocyte cells. In this, the spongocoel opens outside through a circular opening which is quite narrow and is located at the distal end of the body. This is called osculum. It functions like a water canal when water enters through the ostia then into a spongocoel and then moves out through the osculum. It is found in Leucosolenia.

2.Sycon type, (with flagellated radial canals)- It is found in syconoid sponges. The body wall in this type is folded to form radial canals which open into an opening called apopyle. These canals then open into prosopyles. They have the presence of ostia on their outer surface which leads to minute openings called popsicles. The spongocoel in this case is narrow and without flagella and open exterior through the osculum. It is found in Scypha and Grantia.

3.Leucon type, (with flagellated chambers)- In this canal system the radial canal is divided into small rounded and oval flagellated chambers. It is found in leuconoid sponges like Spongilla. The incurrent canals open into flagellated chambers through prosopyles while the flagellated chambers communicate with excurrent canals through apopyles.

4.Rhagon type, (with conical shape and broad base)- It is found in Demospongiae which has conical and tent-like body. The spongocoel is bordered by oval flagellated chambers opening into it by apopyles. Water enters through ostium and enters the incurrent canal. It is a primitive canal system.

Note: The canal system helps sponges in food collection, respiration and excretion.
The flagella of choanocytes beat to produce a water current. Osculum carries food particles and oxygen and sweeps away the metabolic wastes out of the body.