Gemmule Formation

A gemmule is a special kind of internal bud formed only in sponges (Phylum Porifera), such as Spongilla, the common freshwater sponge. It consists of a mass of asexually produced dormant cells called archaeocytes, aggregated together and capable, under the right conditions, of developing into an entirely new sponge. To protect this mass through unfavourable periods, the archaeocytes become coated by a thick, resistant layer of secretion produced by another type of sponge cell, the amoebocytes. Gemmules are thus a survival strategy: they let the sponge tide over conditions such as drought, cold or scarcity of food that would kill the adult body. When favourable conditions of water and temperature return, the gemmule 'hatch …