Reproduction and development Reproduction of sponges is both asexual and sexual. The production of asexual buds can serve as either a means of dispersal and colonisation of new habitats, or for maintaining the existence of the sponge in excessively cold or dry conditions. Most fresh water species produce internal buds called gemmules . These have tough cases, and can exist even after the adult sponge has died. When conditions are suitable gemmules are released into the water for germination in a new habitat.
Marine sponges release external buds after a discrete period of development.
Sponge larvae are free-swimming, and come in a variety of forms. All larvae are covered to varying degree with flagellated cells, which provide their principal means of locomotion. Sponges have a remarkable capacity for regeneration, and asexual budding is frequently a response to damage. Broken fragments of an adult sponge can regenerate by a complete reorganisation of body tissue, and grow into new sponges. This regenerative process is known as somatic embryogenesis .