Scientists discovered an organism with a disappearing butt

The comb jelly—also known as the warty comb jelly, sea walnut, or Mnemiopsis leidyi—has a disappearing butt. Sidney Tamm of the Marine Biological Laboratory in Woods Hole, Massachusetts, told New Scientist that "there is no documentation of a transient anus in any other animals that I know of. It is not visible when the animal is not pooping. There's no trace under the microscope. It's invisible to me."