Since the common carp is primarily a bottom feeder it's mouth pieces and parts have to move a little different than most fish. A smallmouth for instance simply has to come up to it's next meal, quickly open it's mouth and the physics of fluids take over and that minnow or crayfish is deposited right down the throat.
Apparently, how a carp uses it's mouth is of interest to other. Otherwise, why go to the trouble of x-raying one while groping around for food. When you watch this you can see just how easy it is to pull your fly right out of the fishes mouth when setting the hook before he has a chance to get it really close down on the fly. Science is cool!