Trophosome
This organ of dark green-brown spongy tissue is where
the real action takes place. Here, the microbes that
live symbiotically in the worm make their home in
special cells. (Quite a few microbes live here: an
estimated 285 billion bacteria per ounce of tissue.) In
exchange for a safe, cozy place to live, they give the
worm all the food it needs. They do this by absorbing
those three ingredients pumped down from the
plume—oxygen, carbon dioxide, and hydrogen
sulfide—and then controlling their reaction. In
essence, the microbes use the chemical energy released
from the oxidation of sulfide into sulfate to fix carbon
dioxide into the organic carbon that nourishes both the
microbes and the worm. It's a good deal for both
creatures—until, that is, the tubeworm decides to
digest a few microbes for variety. I mean, could you eat
the same meal every day of your life?
