Of all the creatures of the sea, few are as strange and surreal as the sea jelly.
Their most famous feature, of course, is their stinging tentacles. But from there, they get even more unusual.
Contrary to their common nickname “jellyfish,” they are not actually fish. As invertebrates, they have no bones at all. Or teeth, or eyes, or ears. They don’t even have a brain.
And they never sleep.
Sea jellies have been on this planet for more than 500 million years, making them the oldest multi-organ animal on earth.
“It’s an incredibly different animal that is so simple and yet so complex when you start to look more closely,” said Evonne Mochon-Collura. Her official job title at the Oregon Coast Aquarium is the curator of the Fish & Invertebrate Department. Her informal title: “jelly mom.”
Mochon-Collura is the keeper of the sea jellies.
Taking care of sea jellies
Thousands of visitors to the Oregon Coast Aquarium in Newport marvel at the sea jelly exhibit, but few notice Mochon-Collura. She works behind the scenes in a specialized lab set up to raise sea jellies.
She spends her time working in a large room, with a rollup door like what you’d find at a loading dock. It holds bubbling vats of algae, pipes running up walls and across the ceiling and several aquarium tanks, each of different shapes and sizes, filled with jellies.
“They are beautiful and at the same time they can be frustrating from an animal care standpoint,” Mochon-Collura said. “We are not trained specifically for jellies when we go through marine biology degrees in college. So it was a whole new world to me.”
Keeping sea jellies is a relatively new branch of aquarium science. Until the 1990s, it was thought impossible to keep open-ocean sea jellies for any length of time in captivity because they were too delicate for standard aquariums, getting sucked into filters, or ending up stuck in corners, or helplessly bobbing on the surface, while the fine particles of their food sifted to the bottom.
In the wild, sea jellies live in the swirling currents of the open ocean. So aquariums turned to a specialized tank that had been invented to keep planktonic animals alive on research ships. Called a “kreisel,” these tanks take their name from the German word for gyro, or circular turn. Kreisel tanks are often square on the outside, but rounded on the inside, with no corners, to allow the water to flow in a continuous current like a hand sweeping round and round a clock.
Jelly keepers discovered that the non-turbulent flow of kreisel tanks could keep jellies slowly swirling, allowing their bell-shaped bodies to move in their mesmerizing pulse, with their tentacles unfurling, pulling in suspended particles of food.
Climbing a ladder to the top of the large kreisel in her lab, Mochon-Collura gently scooped up a sea jelly. Mochon-Collura noticed lavender clusters under the bell, signaling that this individual is a pregnant female.
She looked through her microscope to confirm. “There are thousands of plangela, or jellyfish larvae,” she said. And with a bright smile, added, “That is fantastic!”
In order to raise jellies, Mochon-Collura had to become an expert in each stage of their life cycle. As if sea jellies were not already unusual enough, their life cycle makes them even more so.
Jellies assume six distinct forms through their life cycle — only one of which actually looks like what people know as jellyfish.
After the larvae have settled, they attach to a hard surface and form polyps — which look like tiny bumps, like those of corals (which turns out, are related to sea jellies). They can stay in this stage for weeks, months or even years.
“Jelly care is a lot of chemistry and physics,” Mochon-Collura said. She monitors the temperature and salinity of her tanks. When conditions are just right, a polyp does something rather amazing: It creates a stack of clones, about a dozen or so, flat and round, almost like a stack of coins.
Then it buds and releases the baby jellies into the water. Each tiny baby has eight arms, looking perhaps more like an octopus than a sea jelly. Eventually, the babies will grow into the shapes we recognize as jellyfish.
Gathering wild jellies
Mochon-Collura has been successfully cultivating her collection of jellies in her lab at the aquarium, but for genetic diversity, and to gather more types of jellies, a team from the Oregon Coast Aquarium sets out from Newport Bay into the Pacific every couple of years to gather jellies from the wild. We tagged along on a recent trip.
Once out in the open ocean, the boat slowed.
“There!” one of the crew members shouted, pointing, as she spotted the shadowy shapes of jellies just under the surface of the dark blue water. Carried by the ocean’s currents, sea jellies are drifters. Where the currents converge, so do jellies. A group of sea jellies is called “a smack.”
The boat operator cut the engine. Two divers slipped on fins and tugged on snorkeling masks and dove from the boat with a splash.
All around the divers are jellies of bright orange and crimson, with long trailing tentacles that look almost like billowing lace. Jellies come in various species, as large as the 120-foot long lion’s mane, or as small as the size of a pinhead. We found a smack of Pacific sea nettles.
The divers scooped up the jellies with their specialized nets that have a fine mesh, which won’t hurt the fragile jellies and can also collect some of the seawater they swim in.
The seawater is not just to transport the jellies — floating in it are unseen gametes. They’re sperm and eggs of the jellies, which Mochon-Collura uses back in her lab.
A diver popped her head above the rolling waves and shouted back to colleagues on the boat, “we’re coming in with three.”
After a few more dives, they’ve collected 18 nettles in all to take back to Mochon-Collura.
Back in the lab
At a table in her lab, Mochon-Collura carefully scooped the jellies out one at a time, combing her fingers through their tentacles, inspecting for small creatures that came with them. Marine animals can often hitch a ride on jellies, like juvenile crabs and small fish. They take advantage of the food particles captured on the jelly’s tentacles.
Mochon-Collura spotted several tiny creatures, so small she needed tweezers to pick them up. One of them had a pale, opaque body and large dark eyes. It squirmed in her tweezers. It’s a parasite that feeds on the flesh of the jellies.
After grooming out all the marine hitchhikers from the jellies, Mochon-Collura slipped them, one at a time, into her largest kreisel.
As they slid from her bucket and into the tank, they joined the current, unfurling, billowing out their bell-shaped bodies, and began to slowly pulse. And pulse. And pulse.
Mochon-Collura paused, empty bucket in hand, and watched.
“I never grow tired of that,” she said. “Whether I’m cleaning a tank, or feeding the jellies, or simply watching them to see what the flows are doing in the tank, I simply can’t take my eyes off of them.”
“I’ve been doing this for over 13 years and I’d love to keep doing this through the rest of my career,” she said, then chuckled, “chances are after I retire, I’ll probably set up a small jellyfish tank at home and take care of them then.”