This jelly Atolla wyvillei has its own natural burglar alarm! In the image on the left, the jelly is shown under white light; in the image on the right, the jelly is in the dark and you can see its “burglar alarm” bioluminescent lights.
This display is called a “burglar alarm” because it is meant to attract attention, just as a burglar alarm does. If the jelly is caught in the clutches of a predator, its only chance of escape is to “call” for help with its eye-catching light display. So it is hoping to attract the attention of a bigger predator that may attack its attacker, thereby affording the jelly the chance of escape.
Learn more about bioluminescence, or the ability of an organism to create light: Ocean Explorer