Gemmulation

Gemmulation is a form of asexual reproduction used by freshwater sponges. It involves the production of gemmules, which are compact clusters of cells, primarily archaeocytes, that become encased in a tough, protective coat. The gemmule serves as a dormant, resilient bud capable of giving rise to a new sponge when conditions are favorable.

Under adverse environmental conditions such as drought, desiccation, freezing, or polluted water, certain sponge cells differentiate and aggregate to form gemmules within the parent sponge. The outer coat of the gemmule is rich in protective materials, including glycoproteins and mucopolysaccharides, and may incorporate skeletal elements such as spicules to increase durability. The gemmule remains dormant until environmental conditions improve. When rehydration and suitable conditions occur, the protective coat breaks down, cells exit the gemmule, and a juvenile sponge regenerates from the liberated cells.

Gemmulation enhances survival and dispersal by allowing sponges to endure periods of stress and to persist in temporary or isolated habitats. Gemmules may be dispersed by water currents or transported by animals, contributing to the colonization of new substrates. This reproductive strategy is characteristic of many freshwater sponges and complements sexual reproduction, enabling populations to persist through fluctuating environmental conditions while maintaining genetic continuity through clonal propagation.