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.[1]

Spongin gives a sponge its flexibility. True spongin is found only in members of the class Demospongiae.[2]


  1. ^ Anderson, D. (2001). Invertebrate Zoology. Oxford University Press. 
  2. ^ Brusca, R.; Brusca, G. (2003). Invertebrate Zoology. Sinauer Associates. p. 191.