Endurance

It wasn't until the fourth week of our voyage that I realized the lump of rock in the cargo hold was alive.  It lifted a leathery head and regarded me solemnly as I maneuvered a grav-cart into place in one of the racks.  I stumbled under the impact of its gaze.

Roarke misinterpreted my surprise.  "They're amazing critters, aren't they?  Live for years on nothing but air and a few drops of water."

"Useful traits for a pet on a long voyage," I ventured.

"Pet?"  Roarke laughed uproariously.  "That's a week of protein there, boy."

The rock-turtle watched us leave.