The Aquarium was one of the first to culture and display live jellyfish, and our new exhibit takes advantage of this know-how. Behind the scenes, Aquarist Tommy Knowles works painstakingly to grow the jellies you see on display, which start as microscopic polyps and are carefully nurtured to their current, three-to-four-inch size on exhibit.Two Growing Operations in One
Looking more like a chemistry class than animal husbandry, Tommy’s lab contains two growing operations in one. First, using a succession of tanks, he nurtures the jellies through their many stages to adulthood.
One part of his lab contains small, horizontal tanks. At first glance, they look empty. But a closer look reveals tiny polyps—cuplike organisms—affixed to every surface. They look nothing like the elegant spotted jellies on exhibit. But within days, the tops of these polyps will break free. Tommy gathers these “ephyrae” using a turkey baster or net and moves them into a larger, two-by-three-foot tank. These ephyrae are kept separate and protected in floating bowls or "critter keepers."
Soon they’ll begin to resemble actual jellies, reaching a size of about an inch after just one month. At this point they’re free to swim about the tank, and they start to change from a brown color to the beautiful blue hue you see on exhibit.
In a separate growing operation, Tommy is rearing tiny brine shrimp, or nauplii, to feed the jellies. This involves a bleaching process to ensure no foreign organisms are introduced along with the “naups,” as he calls them.
“I’m harvesting naups everyday,” says Tommy. “So I’m rearing two organisms: I’m feeding algae to the naups, and feeding naups to the jellies.”
In addition, each jelly grows a crop of algae in its tissues, called zooxanthellae. Waste products from these algae are another food source for the jellies. This “symbiotic” relationship requires plentiful light—up to 1,000 watts—for the zooxanthellae to grow inside the jellies.“Groundbreaking Husbandry”
We’re among the few aquariums in the world that have permanent displays of jellies, and it’s not hard to understand why. It’s a complicated process that requires constant vigilance. “We grew spotted jellies for our ‘Jellies Living Art’ special exhibition that closed in 2008,” says Tommy. “It was groundbreaking husbandry at the time, and we’re picking up where we left off. The largest spotted jelly was 16 centimeters across, and it would be great to reproduce that.”For Tommy and the rest of the husbandry staff, it’s a lot of work, but it’s worth it. “I love this species. They have high metabolism and they grow quickly, which means you can see the products of your efforts quickly. It’s challenging and delicate, but it’s fun.”