The Animal That Swallows Its Own Fuel

Green hydras survive by hosting tiny algae inside their own cells. To keep these microscopic tenants alive, the hydra actively shuts down parts of its own immune system.

This microscopic creature essentially treats its own body like a greenhouse for green algae. By disabling its natural defenses, the hydra allows the algae to thrive and provide it with nutrients through photosynthesis. It is a fascinating case of an animal compromising its biological protection to form a permanent, energy-producing partnership. This unique relationship helps scientists understand how complex life forms learned to live together millions of years ago.