Question

describe three types of canal system in porifera

Answer 1

Hello friend
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The arrangement, and complexity of the canal system varies considerably in different sponges and has been divided into four types :

1.         Ascon type

2.         Sycon type

3.         Rhagon type

4.         Leucon type

Ascon type:

It is the simplest type of canal system in which the body is thin-walled, radially symmetrical and hollow due to the central cavity. This cavity is known as the spongocoel or paragastric cavity that opens to the outside by means of a circular aperture (known as osculum) at the free distal end of the cylinder. Numerous minute pores the ostia are also present in the thin wall of the cylinder.

Sycon type

It is more complcx system as it is folded version of the asconoid body. It is found in Scypha and the embryonic development of Scypha clearly shows the asconoid type by the outpushings of the wall of an asconoid sponge at regular intervals into finger-like projections called radial canals.

Rhagon type

This type of canal system is found in the larva of Demospongiae called rhagon which has a broad base and is conical in shape. Due to excessive growth of mesenchyme sub-dermal spaces are formed in its body wall. The ostia open in these spaces which lead into incurrent canals.

Leuconoid type

This type of canal system is formed from the rhagon type by the outfolding of the choanocyte layer.  In this type, oval or rounded chambers lined by flagellated cells are formed by evagination of the radial canals.
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