Stubb with a section of sponge from the specimen below

 

Sponge - complete with algal strands - washed up on a New Hampshire beach

Spicules serve as a framework to support the soft cellular material of the sponge. The spicules keep the pores of the sponge from collapsing and allow this animal to grow to considerable size. The spicules may be composed to a soft protein material or harder substances like calcium carbonate or silica.