The xxeljet replaced its ancestor the probojet. It has grown twice its size and has developed a collection membrane between its four-jawed needle mouth. Now it can both harpoon prey as well as collect large amounts of plankton to eat. It also still has its second mouth in which has a primitive jaw. This is uses to chew up prey it cannot otherwise chew with the other toothless mouth. It is now on a stalk which can be maneuvered to eat. Like its ancestor it has a methane producing chamber in which not only used for buoyancy when swimming but can be used as a jet when escaping predators such as the marollon. The methane is produced as a byproduct of digestion. Their primitive eyes have evolved into a compound eyes which can pick up the faint light given off by bioluminescent creatures such as the dark swarmers.