Britannica Sources used in this answer

How do freshwater sponges survive drought and freezing?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

The image shows a group of Virginia big-eared bats sleeping upside down in a dark cavern. — Dormancy Virginia big-eared bats (*Corynorhinus townsendii virginianushibernating*) are true hibernators, entering a state close to death for much of the winter.

Freshwater sponges survive drought and freezing temperatures through a process of asexual reproduction known as gemmulation.1

During periods of environmental stress, these sponges produce specialized structures called gemmules. These structures consist of aggregates of cells—primarily archaeocytes—laden with reserve food granules. To provide protection, these cell masses are surrounded by membranes that are often reinforced with spicules.12

The survival mechanism functions as follows:
* Suspended Activity: Gemmules allow the sponge to enter a state where vital activities are almost completely suspended.1
* Seasonal Adaptation: In cold regions, gemmulation occurs in winter (hibernation), while in warm regions, it occurs in summer (estivation).1
* Regeneration: When favorable conditions return, the gemmules germinate. The archaeocytes emerge through an opening called the micropyle, allowing the cells to differentiate and grow into a new sponge.12

This process ensures the species can persist even when the adult sponge dies and disintegrates due to harsh conditions.12