Phylum Porifera

Phylum Porifera (Latin porus = pore, ferre = to bear) includes the sponges — examples include Scypha, Euspongia (bath sponge) and Euplectella (Venus' flower basket). They are aquatic animals, mostly marine with a few freshwater forms, and are sedentary, remaining fixed to a surface throughout adult life.

Most sponges are asymmetrical and follow the cell aggregate body plan: cells cooperate loosely rather than forming true tissues, so the body functions almost like a colony of different specialised cell types.

The body surface bears numerous tiny pores called ostia, through which water enters an internal cavity called the spongocoel; water then leaves through a single large opening, the osculum. This directional water flow, driven by the canal system, is how sponges feed, respire and excrete — as water circulates, cells lining the canals absorb food particles, exchange respiratory gases, and release excretory waste directly into the passing water.

The spongocoel and canals are lined by flagellated cells called choanocytes (collar cells); the beating of their flagella drives the water current through the body.

The soft body is given mechanical support by a skeleton of calcareous or siliceous spicules, or by a network of proteinaceous spongin fibres (as in bath sponges). …