Spongillidae

Spongillidae is a family of freshwater sponges within the class Demospongiae (phylum Porifera). Members are distributed worldwide in lakes, rivers, ponds, and other still or slow-moving freshwater habitats, attaching to submerged surfaces such as rocks, aquatic plants, or man-made substrates. The family includes several genera, most notably Spongilla, and is characterized by life history traits typical of freshwater sponges, including gemmule formation in some species.

Anatomy and skeleton: Like other sponges, spongillids are sessile, filter-feeding organisms with an aquiferous system driven by choanocytes. Their skeleton is largely siliceous spicules embedded in a collagenous matrix, with spicule shapes varying among taxa. The canal system can range from simple to highly developed leuconoid forms, which support efficient filtration in aquatic environments.

Reproduction: Spongillids reproduce both asexually and sexually. Asexual reproduction occurs by budding and fragmentation; a distinctive feature in many freshwater species is the production of gemmules. Gemmules are resistant, dormant aggregates containing archaeocytes surrounded by protective layers of spicules and organic material, enabling survival through freezing or drought and enabling rapid post-stress recolonization. Sexual reproduction is common, with many sponges being hermaphroditic; eggs and sperm are produced within the sponge, and free-swimming larvae disperse before settling to form new individuals.

Ecology: Spongillids function as important filter feeders, contributing to water clarity and nutrient cycling. They often form colonies on substrates and can influence community structure on local scales. Their presence and abundance are frequently used as indicators of freshwater quality.