Spongin

Spongin is a family of proteinaceous materials that forms the fibrous skeleton of many sponges (phylum Porifera). It is a collagen-like polymer that creates a flexible, porous network supporting sponge tissue and helping maintain the organism’s shape in flowing water.

Spongin fibers are typically soft and elastic, enabling sponges to bend and recover their form. The proteins are cross-linked to form a resilient network and are distinct from mineral skeletal components. The exact composition of spongin varies among sponge species, and in many sponges it occurs alongside siliceous or calcareous spicules, while in others the skeleton is primarily spongin-based.

Distribution and variation: Spongin is most closely associated with demosponges, including species used to harvest commercial bath sponges. Freshwater sponges also produce spongin, often in combination with silica spicules. In some sponges, spongin provides the main structural framework; in others it complements mineral skeletons.

Functions and properties: The spongin network supports filtering structures and creates the sponge’s characteristic softness and lightness. Because of its proteinaceous nature, spongin is relatively resilient to water loss and can be more flexible than rigid mineral spicules, influencing the physical texture of the sponge.

Uses and significance: Historically, natural sponges made from spongin were widely used for cleaning and bathing. In modern times, spongin remains of interest in studies of biopolymer materials due to its biocompatibility and elastic properties.

See also: sponge skeleton, spicules, collagen.