The Jelly Lifecycle
For simple animals, jellies have a complex lifecycle beginning in the simple polyp stage and maturing through the adult or medusa stage. Many jelly species hatch from eggs into free-swimming larvae known as planula, which eventually settle on a hard surface, like a seashell, and transition to a stationary polyp stage. Jelly polyps resemble miniature sea anemones. From here, when environmental conditions are right, the polyp will undergo "strobilation," where ephyra, resembling a stack of microscopic dinner plates, form. Tiny free-swimming ephyra are then released one by one into the water column where they eventually grow to the adult medusa stage. Polyps can also bud off to produce more polyps, so some jelly species can reproduce both sexually and asexually. In the case of box jellies, a juvenile jelly grows into a two-tentacled medusa before third and fourth tentacles grow congruently from the medusa bell (or "pedalium") and increase in size toward adulthood.
Back in 2016, Jennie Janssen noticed something peculiar in the Camouflaging exhibit in the Surviving Through Adaptation gallery. On the water's surface, she spotted a transparent, barely visible jelly about 5 millimeters in length. Considering the Camouflaging exhibit is not jelly-centric, this was a shocking find!
Over the following weeks, more jellies were spotted on exhibit and moved to the National Aquarium's Culture Lab for closer examination. Under a microscope, it was clear to Aquarium staff that these were box jellies, but determining their exact species proved to be a challenge.