Spongin, a modified type of collagen protein, forms the fibrous skeleton of most organisms among the phylum Porifera, the sponges. It is secreted by sponge cells known as spongocytes.
Spongin gives a sponge its flexibility. True spongin is found only in members of the class Demospongiae.
- ^ Anderson, D. (2001). Invertebrate Zoology. Oxford University Press.
- ^ Brusca, R.; Brusca, G. (2003). Invertebrate Zoology. Sinauer Associates. p. 191.