Osculum

: oscula) is an excretory structure in the living sponge, a large opening to the outside through which the current of water exits after passing through the spongocoel.

Sponges pump large volumes of water: typically a volume of water equal to the sponge's body size is pumped every five seconds.

Its size, in turn, is one of the factors which determines the amount of water flowing through the sponge.

It can be closed completely in response to excess silt in the water.

This poriferan- (or sponge-) related article is a stub.