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Keeping Moon Jellies

Posted on Mar 2, 2016 by in Animal Care


Look up and inside of the smokestack of the old powerhouse you will find a chimney full of Moon jellyfish. A lot of work and care goes into maintaining this unique exhibit. Here’s a quick look at what goes on behind the scenes of our jellyfish exhibit.

Jellyfish Life Cycle
Photo: Jellyfish life cycle…Jellies have a very unique life cycle in that they reproduce through both sexual and asexual reproduction.

Culturing Jellyfish
We are happy to say that all of our jellyfish have been cultured right here at the GCA! We keep several plates of jelly polyps in flow through bins to catch and collect ephyrae. When the polyps asexually reproduce, they go through a process called strobilation. Once the ephyrae (stage 5 of the jellyfish life cycle) break off from the strobila they are pulled through to the bottom collection bin. There are several methods used to induce the strobilation process. The best way we’ve found here is through dramatic temperature swings. Dropping the temperature by 10-15 degrees for about 7-10 days has the polyps strobilating in no time! Once the strobilation process begins, we will find about 50-100 new epyrae each day. As the ephyrae slowly grow into medusa they will be moved into an appropriately sized tank and eventually make their way up to the chimney display. This process will take about 2-3 months.

Moon Jelly Culture
Photo: Moon jelly culture set up at the Greater Cleveland Aquarium

Jellyfish Exhibit Design
Jellyfish are not very good swimmers and rely on ocean currents to get around. This means that the exhibit design and flow is very important when keeping jellies in aquariums. Jellyfish are typically kept in a round shaped exhibit, called a kreisel or pseudokriesel. The round shaped exhibit with a spray bar, help push the jellies in a circular motion to keep them suspended off the bottom.

Photo: Pseudokreisel built at the Greater Cleveland Aquarium

Jellyfish Diet
In the wild, most jellyfish eat zooplankton. Zooplankton is made of many tiny aquatic animals. Adult brine shrimp (Artemia nauplii) are most commonly used for captive diets. Unfortunately, adult brine shrimp don’t have much nutritional value for jellyfish but juvenile brine shrimp are. Our jellyfish are fed 48 hour hatched Artemia twice day that are enriched with a concentrate algae diet. They are also fed a krill shake once a week for variety. The idea of a krill shake is to blend up a mix of large, nutritious fish chucks that would normally big too large for the jellies to eat.

Artemia Nauplii
Photo: Artemia nauplii culture set up at the Greater Cleveland Aquarium

Don’t Moon Jellies Sting?
Although there are species of jellies that can have a fatal sting, the sting of a moon jelly is incredibly mild. A sting from a moon jelly usually results in an itchy, red rash and not considered a danger to humans. Here at the aquarium, we keep a spray bottle of diluted vinegar nearby to help stop and neutralize the sting.