The Mediterranean jelly (Cotylorhiza tuberculata) is one of my favourite jellyfishes on display at the Vancouver Aquarium, mostly because it looks like it has sweet little gumdrops hanging off its body. But not only does it look neat – the story of how we grew them for display is also fascinating.

When Aquarium biologist Tak Oyama was first told about the plan to display the Mediterranean jelly at the Aquarium, he jokingly says he thought this would mean a trip to the sun-soaked beaches of Europe. Alas, the real plan was to obtain the polyps of these jellyfishes from another aquarium and culture them here.

After the polyps arrived from an aquarium in Japan, Vancouver Aquarium’s jellyfish crew did a lot of research. They found out the conditions needed to stimulate the polyps so they would produce offspring – this process is called strobilation. It’s one of the asexual ways jellyfishes have babies.

A jellyfish so nice, I'm showing it twice.

A jellyfish so nice, I’m showing it twice.

Jellyfishes have complicated life cycles. They reproduce sexually, releasing sperm and eggs that form polyps, while the polyps themselves reproduce asexually – either cloning to produce more polyps, or strobilating to produce the next generation of jellyfish.

Although Mediterranean jellies are quite abundant in their natural habitat, Tak says they’re not so common in aquariums because they are tricky to culture and maintain. So he was elated when he and the crew got the conditions just right for the polyps. When he saw strobilation happening, he was so excited that he felt the urge to share the good news with his fellow jelly biologist, even though it was her day off.

“When I saw strobilation happening, I texted Mackenzie right away!”

Tak has been impressed with their growth thus far, saying, “I’ve never seen a jellyfish grow that fast.” A month ago, the jellyfish were the size of a pencil eraser. Now, they’re the size of a chicken egg. Eventually, they may grow to be bigger than a piece of letter-sized paper.

See the Mediterranean jelly, and others from around the world, as part of the new exhibit Jelly Invasion, on until November 12.

Written by Karen Horak, writer-editor, content and digital experience at the Vancouver Aquarium.

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