Four and twenty mussels ...

Yesterday I was asking, "Do flatworms eat barnacles?"  I've been searching for an answer, without much success. The websites I visited mention mollusks, especially oysters, other worms, and dead organisms, but don't differentiate between different flatworm species.

I wanted more info. The real question I was asking was, "What specific animals does this species of flatworm eat? And how did mine grow so fast?" And I kept remembering the giant worm that was destroying coral in a UK aquarium. Could my little tank support a "voracious predator"? Would it attack my clams? Or my one big thatched acorn barnacle?

Laurie suggested I remove the flatworm from the aquarium. So, for the third time running, I emptied the tank. This time, I sifted the sand, counted all the live critters I found, removed empty shells. I found only one flatworm. Whether the other died, or is hidden too well (remembering how it disappeared inside the shell of a live barnacle), I don't know. At least I captured one.

And I think I might have found out what he has been eating. I counted 24 empty mussel shells.

Corpora delicti

That's a lot of mussel meat in 40 days!

But maybe I'm jumping to a conclusion too soon; it's possible that something else killed them and then the hermits and crabs emptied the shells. So I've confined the flatworm to a canning jar, added clean sand, sea water and, reluctantly, one healthy mussel. Give him enough rope ...