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?
