Canal System - Porifera
CANAL SYSTEM - PORIFERA A. Definition. A system of connected cavities found in a sponge body is known as the canal system. B. Types . There are three main types of canal system. These, in order of increasing complexity, are asconoid, syconoid and leuconoid. 1) Asconoid Canal System This is the simplest type of canal system. It is found in Leucosolenia . Its important features are enumerated below- (i) The sponge wall is thin and unfolded. (ii) The mesenchyme is feebly developed. (iii) The ostia lead directly into the spongocoel. An ostium is intracellular, i.e., it is a passage through a tubular cell called the porocyte . (iv) The spongocoel is large and lined all over by choanocytes. It opens out by a single terminal osculum. (v) The route followed by the water current includes ostia, spongocoel, and osculum. The asconoid canal system occurs in only a few sponges. The sponges with such a canal system are small in size and have a radially symmetrical, vase-like body. 2) Syconoid Canal