How do sponges use gemmules to reproduce during unfavorable conditions?

Sponges utilize a process called gemmulation to survive environmental stressors such as drought or extreme temperatures. During this process, aggregates of cells—primarily archaeocytes laden with reserve food granules—become isolated and encased in a protective, often spicule-reinforced covering.1

These gemmules allow the sponge to enter a state of dormancy where vital activities are suspended. In freshwater sponges, this may manifest as hibernation during winter or estivation during summer. When the adult sponge dies and disintegrates, these resistant structures are released into the environment.12

Once favorable conditions return, the gemmules germinate. The archaeocytes emerge through an opening known as the micropyle, differentiate into various cell types, and develop into a new sponge.12