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. Because of this, indentification from photographs can become very difficult.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). Many sea sponges can only be identified by the microscopic examination of the skeleton. Spicules consist of a mesh of protein called spongin. The "skeleton" of a sea sponge is made up of tiny needlelike splinters called spicules. Water moves through the canals, into the chambers, and out through the central canal and osculum. These sponges consist of masses of tissue penetrated by numerous canals, all of which lead to a number of smaller chambers lined with flagellated collar cells. Leuconoid sea sponges are the largest and most complex. The collar cells' flagella work to force water into the spongocoel and out through the osculum. The syconoid body wall is thicker and the penetrating pores are longer, forming a system of simple canals lined by collar cells. Syconoid sponges tend to be larger in size than asconoids and have a tubular body with a single osculum. The opening of the tube, called the osculum, leads to the spongocoel, the inner region of the tube. Asconoid sponges are tube shaped and perforated by spores. Sea sponges have three different body plans: asconoid, syconoid and leuconoid.
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