Spore

The biologist looked at a spore under the microscope.

Thresher maws are subterranean carnivores that spend their entire lives eating or searching for something to eat. Threshers reproduce via spores that lie dormant for millennia, yet are robust enough to survive prolonged periods in deep space and atmospheric re-entry. As a result, thresher spores appear on many worlds, spread by previous generations of space travelers.