Jellyfish are such odd creatures, so is their name since they aren’t fish at all. They don’t have scales, or gills, or fins; which is why most aquarists and biologists will refer to them as sea jellies.
In addition to lacking basic fish parts, they also lack a heart, a brain, muscles, and blood! They have a thin skin that holds together all their jelly, or mesoglea, and they can absorb oxygen right through their skin.
Moon jellies are very common and found in most of the world’s oceans. They can be recognized by the four horseshoe-shaped organs at the pinnacle of their bell. These organs function as both their stomach and their gonads, how efficient!
Now that you have some basic knowledge, I’m going to take you behind the scenes yet again, and show you where baby moon jellies come from and how we grow them in house.
Jellies can live a long time in aquariums and that’s because we keep them in close to ideal conditions. They are usually kept in round tanks not only to keep them from getting stuck or ripping open their bell on anything but also because they are not strong enough to swim against even a small current.
Jellies are the world’s biggest plankton! The exhibit tanks never have air bubbles because jellies are prone to air embolisms. And of course, we give them a healthy and consistent source of food.
Jelly life cycles are a tad complicated, so I’ll try to break it down and simplify it. Sea jellies are those big bell-shaped creatures that you love to look at in aquaria, and those jellies can be a male or a female. They will release eggs and sperm that come together and form a tiny zygote called a planula.
Now here’s the crazy part that most people don’t know, that planula settles to the bottom and becomes a tiny pink anemone known as a polyp.
These polyps then recreate a-sexually, called strobilation, to create a stack of baby jellies on their bodies, called ephyrae. Once these ephyrae pop off and enter the water column, they will feed on passing microplankton until they are big enough to develop a bell and be considered a medusa, which is the sea jelly most people think of. That process wasn’t to bad right?
I started by taking polyps that were naturally settled in the exhibit and getting them to settle in my designated polyp tank.
Image by Dani Jensen
These polyps were then encouraged to strobilate and create little stacks of ephyrae.
Image by Dani Jensen
Once the ephyrae are floating freely, I keep them in small round tanks that have a circular flow. I feed them twice daily and watch them grow! This is the best part because they start to look so vastly different in a short amount of time.
Feeding time is also especially fun at this stage because you can see the tiny jelly bellies filled with the microscopic orange shrimp that we feed them.
Image by Dani Jensen
Culturing moon jellies is quite easy once the process is going. This practice is also more environmentally friendly because it reduces the number of animals taken from the wild and reduces the carbon emissions used in shipping these animals. Next time you stop by your local aquarium, you’ll know so much more when you stop to admire the jellies!
