Described as mesmerizing, beautiful, even otherworldly, jellies are unique in the animal kingdom. Not technically fish, they have no heart, brain, blood or bones and are 95 percent water.
Most closely related to corals and anemones, their pulsing translucent bodies drift an unchoreographed dance based mostly on water currents, not choice.
The full life cycle of these incredible animals actually takes place at the Aquarium, as baby jellies grow up and are cultured by skilled aquarists in what is referred to as the jellies lab.
Bringing Up Jelly
Jennie Janssen, Manager of Changing Exhibits, is in charge of the jellies lab, located on Pier 5 in the Institute of Marine and Environmental Technology, and Jellies Invasion: Oceans Out of Balance on Pier 4 inside the National Aquarium.
Janssen and her team of aquarists are responsible for many species, including moon jellies, lion’s mane jellies and Atlantic sea nettles.
In the lab, the Jellies team cares for a community of jellies, raising them until they are large enough to go on exhibit. Sometimes there are hundreds of babies being cultured, at other times as few as five or six.
During a visit to Jellies Invasion, guests can sometimes see what look like baby jellies pulsing alongside the adults, but in fact they are more like teenagers. Jelly babies are extremely small, developing from tiny polyps (resembling small sea anemones) that attach to the inside of their exhibits.
Polyps are collected from exhibit walls and viewing windows and allowed to attach to petri dishes in the lab. There, they are fed, kept clean and encouraged to strobilate, releasing free-swimming ephyrae. At just 2 millimeters, these ephyrae are easy to miss, except by those with a trained eye.
Once the ephyrae are released, they ride the water flow into a larger container where they grow until they are big enough to be put on exhibit.
There’s No Place Like Home
While specific jelly species have different exhibit needs, they are generally cared for in the same ways. Jellies eat zooplankton, small fish and other jellies in the wild. Jellies at the Aquarium eat brine shrimp, grown by the Jellies team, two or three times per day. As the jellies grow, their food gets larger as well.
A precise balance of water flow, salinity and temperature is critical to a viable jelly-breeding program, and sophisticated water measurement technology allows aquarists to keep careful watch over the conditions.
The size and shape of the tank, in addition to the direction and speed of water flow, are important in ensuring the jellies don’t rub against the walls or become tangled. The aquarists on staff are constantly tweaking the instruments and engineering the tanks to make sure that flow is perfect for these drifters.
In fact, Janssen says that getting that water flow rate just right is one of the hallmarks of a great jelly aquarist. And the Aquarium’s Jellies team is among the best. Not only do aquarium-raised jellies appear on exhibit here in Baltimore, but many are sent to other aquariums for their exhibits…kind of like a jellies invasion!