Most of us know that sponges are filter feeders, but some of us (and a large portion of the general public) think of sponges as passive organisms that essentially soak up food like, well, a sponge. Nothing could be further from the truth!
Sponges actively pump water through their osculums (AKA “little mouths”) by using an army of tiny flagella (threadlike appendages) flapping like microscopic madmen to push water through the sponges’ chambers.
The drawing to the right by the Marine Education Society of Australasia shows how this mechanism works. And the video below shows how efficiently sponges can process large volumes of water through their systems.