spongocyte

Spongocyte is a specialized cell type in sponges (Porifera) that synthesizes and secretes spongin, the organic component of the sponge skeleton in many demosponges and some other sponge groups. The spongin fibers form a fibrous network within the mesohyl that provides structural support and, in many species, flexibility to the body wall and canal systems.

Spongocytes arise from amoeboid mesenchymal cells such as archaeocytes and reside in the mesohyl, the gelatinous middle layer between the outer pinacoderm and the choanocyte chambers. Morphologically they are elongated or spindle-shaped and contain abundant cytoplasm rich in rough endoplasmic reticulum and Golgi apparatus, along with secretory vesicles containing spongin precursors.

Function: The main role of spongocytes is the production and secretion of spongin proteins, which assemble into a cohesive skeleton. Spongin can occur alone, or in combination with mineral spicules in some species; in sponges lacking silica or calcium carbonate spicules the spongin network provides the primary framework. Spongocytes may participate in wound repair and regeneration by contributing to the mesohyl matrix.

Taxonomy note: Spongocytes are not a taxonomic group but a cell type within the sponge body plan and are studied in sponge histology and developmental biology.