I've just noticed that one of my Amanos looks quite different internally to the others. There is a long brownish thing in the top part of its body, just below the stripe on its back. I'm concerned it could be some sort of parasite, although a Google search didn't show me anything that looked similar to this. I've attached two photos, the first is of a "normal" shrimp and the second is the one I'm worried about. Any ideas what it could be?