Spongin

Spongin is a type of collagen protein that forms the fibrous skeleton of most organisms among the Phylum Porifera, the sponges.

Spongin does not make up spicules. Spicules can be calcareous or siliceous depending on taxonomic Class; spicules form the rigid skeleton of sponges (Phylum Porifera) as well as offer protection from predation. Spongin is a protein made of modified collagen, it gives a sponge its flexibility.

Spongin