This is kind of like asking "what are my chances?", because no one really knows exactly what will be asked. Could the DAT ask you a question that pertains to the operculum? Sure. Is it super likely? Probably not. I can say that on my DAT, I had no questions that asked me to recall minute details about animal anatomy, other than humans. I bet after making this thread, though, you'll never forget what an operculum is... So for your sake, I hope it pops up on your exam! Haha. In all seriousness, start with the big picture, then work inwards for as long as time will allow.