Untangling comb jelly culture
Try as she might, MacKenzie Bubel just couldn’t satisfy the baby comb jellies.
The aquarist was attempting to spawn a species called Mnemiopsis leidyi—ghostly-looking little creatures native to the Gulf of Mexico—in the Aquarium’s Jelly Lab. She tinkered with variables like water temperature, salinity and light exposure.
“We did some wacky stuff to get the conditions perfect,” she says, “but they weren’t doing as well as we’d hoped.”
That changed when our staff aquarists, in collaboration with University of Miami assistant professor William Browne, pioneered an efficient way to culture comb jellies en masse. The breakthrough—which we’re sharing with our colleagues—could eliminate the need for aquariums to collect comb jellies from the wild. It could also pave the way for deeper scientific study of these little-understood animals.
One weird trick
Senior Aquarist Tommy Knowles first began culturing comb jellies in 2012. His early attempts were mostly unsuccessful, but they provided a foundation for his team to build on.
The “aha” moment came in March 2015, when Senior Aquarist Wyatt Patry joined a Monterey Bay Aquarium Research Institute (MBARI) expedition, led by marine biologist Steve Haddock, in the Gulf of California. William Browne was also on the boat, studying comb jellies from an evolutionary biology angle.
“Literally within 10 minutes of meeting, we delved into Mnemiopsis culturing,” Wyatt says.
In our exhibits, the aquarists had been feeding adult comb jellies (which are hermaphroditic) baby brine shrimp and tiny crustaceans called copepods. But William told Wyatt the key to keeping baby comb jellies alive is to feed their parents larval fishes.
Wyatt quickly got in touch with MacKenzie and advised her to switch the comb jelly feed to newborn zebrafish. Suddenly, MacKenzie’s innovative spawning methods worked.
“As soon as we started feeding the adults larval fish, we had super-healthy adults, and the quality and quantity of embryos exploded,” she says.
Where previous efforts had produced on the order of 10 baby comb jellies, the team was now spawning hundreds—even topping 1,000 at one point.
“We grew so many that we had to find homes for them all,” Wyatt says. “Then we started applying the methods to other species.”
The Aquarium team worked with Browne to develop a protocol. They’re now co-authoring a paper they hope will make it easy for other scientists to culture comb jellies.
After spawning three generations of Mnemiopsis in the Jelly Lab, the Aquarium team moved on to other species of comb jellies. The new method worked beautifully for Bolinopsis infundibulum, on display in the Aquarium’s Drifters gallery, and Pleurobrachia bachei.
The approach paves the way for scientists to study comb jellies, also known as ctenophores, at a larger scale.
In wild studies, scientists can only observe “snapshots” of comb jelly life. Using the new lab culturing method, they can study the animals through their whole life cycle. This could help researchers better understand comb jelly behavior in places like the Black Sea, where invasive Mnemiopsis have decimated fish populations.
“We don’t know what all their ecological roles are in the wild because comb jellies are so under-studied,” Wyatt says.
George Matsumoto, senior research and education specialist for MBARI, says the collaboration between the Aquarium and the University of Miami could affect the way scientists think about evolution.
“Comb jellies are getting much more attention these days because of work in the past 10 years tracing the ancient ancestor to all living things,” he says. “We don’t have a good idea of what this ancestor looked like, but the first group of animals diverging from the tree of life looks like the ctenophores.”
Another potential benefit of the breakthrough: testing how comb jellies react to temperature and pH changes. As people continue to burn fossil fuels, the ocean is warming and becoming more acidic. Some species are likely to adapt quickly; others might not.
“Now that the Aquarium has been able to put these animals in culture,” George says, “it’s possible we could try to answer some of those questions.”
Featured photo: Comb jellies in The Jellies Experience, a special Aquarium exhibition open from 2012-2014. Photo © Charlene Boarts.