Water enters through short canals or directly through openings (ostia) into the chambers and leaves through a single outlet (apopyle) to the atrium and from there out of the osculum.
Syconoid forms, in turn, possess many ascon-shaped cylindrical chambers branching off a central cavity (atrium). Insets show zoom-in water path (blue arrows) into the chambers in sycons and leucons, where in the latter, water is forced to go through collar filters (black) of choanocytes (red, cc) due to the presence of a physical gasket (g).Īsconoid forms are organized as a single tube in which the choanocytes form a single layer on the inner surface of the tube wall. Schematic of sponge body types in ascon (A), sycon (S), and leucon (L) with evolutionary view of grades of morphological complexity in calcareous sponges (black arrows).
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