A clam whose shells have been re-engineered as drill heads also has dozens of mini-teeth that scrape rocks for food, ingesting and breaking them down. Most shipworms, as they are called, eat wood:
Like other shipworms, the rock-eating shipworm still ingests what it scrapes away to make its protective burrow, but it lacks both the sack and its bacteria and likely doesn’t get much sustenance from the rock bits. Their ingestion may be a holdover from wood-eating ancestors. Instead, it seems to rely on other bacteria residing in its gills to produce nutrients or food sucked in by a siphon at the clam’s back end for nourishment.Elizabeth Pennisi, “This rock-eating ‘worm’ could change the course of rivers” at Science (June 18, 2019)
Hmm. Another way of looking at this: It probably picks up a lot of bacteria while busting up the rocks. And it puts them to work. Mergers and acquisitions, as they say in business.
Paper. (open access)