When she made a discovery that thrilled her fellow divers and thrilled researchers across North America, she didn't think much of it at first.
“I just thought, oh, this is a rotten leaf, keep going,” says Ellie Oftenort.
The avid scuba diver passed by this “black stuff” once or twice, but it wasn’t until the third pass that something caught her attention enough to take a closer look and she realized it was a living creature.
“I just started screaming, there’s a sea slug!”
Oftenort's mother, who was on shore at Rainbow Haven Provincial Park near Dartmouth, N.C., turned on a snorkeling group chat, and within minutes, members identified it as Elysia chromotica, or Eastern emerald Elysia.
This unassuming creature could pass for the common slug that destroys your salad every summer. That is until its wrinkled back unfurls a stunning emerald green “leaf” with pale “veins” radiating outward from the center.
It is this “leaf” and what it does to the sea slug that holds great promise for research in the field. medicine, clean energy and other areas.
But it is so elusive that it is difficult for researchers to study it.
Elysia chromotica can photosynthesize by stealing chloroplasts—the photosynthetic organs—from the algae it eats, keeping them alive in its body and using them to obtain energy from the sun. Sea slugs can survive for months without consuming food.
“It's like if I ate a whole bunch of spinach and then woke up this morning and just sunbathed for an hour, and then I didn't have to eat for the rest of the week,” says Hunter Stevens, a biologist with the Nova Scotia branch of the Canadian Parks and Wildlife Society. “These slugs are essentially doing the same thing.”
Although the ability to photosynthesize is rare in the animal kingdom, Elysia chromotica is not unique in this regard. Other sea slugs can do this too, but not nearly as well as Elysia chromotica.
“Elysia chromotica is kind of the reigning world champion,” says Patrick Krug, a biological sciences professor at California State University, Los Angeles, who studies marine invertebrates. for decades.
Krug says researchers don't know how long Elysia chromotica can go without eating.
He says that all the other species he has worked with in the laboratory gradually fade away and become unable to support chloroplast life.
“Chlorotica doesn’t do that,” Krug says. “I had them in my lab once, and I never saw them turn anything other than green. They were bright green for as many months as I kept them, just living in the light, and they never ran out.”
Potential Research Applications
Researchers want to figure out how Elysia chromotica does this job so well, and hope that unlocking its secrets could ultimately help people.
The discoveries could someday lead to advances in wound healing, energy and nutritional supplements, drug therapies, cleaner energy technologies and biophotovoltaic cells, the scientists say.
Joshua Widhalm is an assistant professor of horticulture and director of the Purdue Indiana Center for Plant Biology. For the past six years, he has been studying another species of photosynthetic sea slug—Elysia crispata, commonly called the salad sea slug—because Elysia chromotica is so difficult to find and preserve.
He says that unlocking the secrets of how these creatures steal chloroplasts, incorporate them into their own cells and keep them functioning could have implications for everything from vaccines to chemotherapy drugs to herbicides and pesticides, which are expensive to synthesize.
Additionally, since the process of photosynthesis produces oxygen, understanding how sea slugs protect themselves from or get rid of excess oxygen could advance research into human inflammatory diseases, neurodegenerative diseases, cancer or even age-related conditions, Widhalm says.
“Imagination is the limit,” he says.
Elusive and ephemeral
However, this coveted bullet perfectly eludes researchers.
Historically known populations existed in the Minas Basin region of Nova Scotia and Martha's Vineyard in Massachusetts—and their habitat theoretically exists along the entire east coast of the United States—but recent efforts to find them have been unsuccessful.
“For a long time, it seemed like no one had seen them,” Krug says. “It was such a shot in the dark that it wasn’t even worth watching.”
Dylan Gagler, a graduate student at the American Museum of Natural History in New York, has searched the slug's favorite habitat off Martha's Vineyard multiple times this year, but so far has been unsuccessful.
When Stevens' Instagram post about Rainbow Haven's opening appeared on Gagler's feed, he says he was “mad, FOMO.” [fear of missing out] moment when I need to get to Nova Scotia. Like, this is where all the action happens.”
Gagler contacted Stevens to obtain information about conditions in the Rainbow Haven area, such as air and water temperatures, and the depth at which they were found, to refine his own search. He is also exploring the process of obtaining permission to collect samples from Nova Scotia for laboratory cultivation.
Although Elysia chromotica has been difficult to find, Krug says there have been several sightings in recent months, including in Nova Scotia, as well as in the Carolinas and Tampa Bay, Florida.
He says the population is “ephemeral”, appearing to go through boom and bust cycles – sometimes in abundance but then suddenly disappearing.
Requires a certain habitat and nutrition.
Elysia chromotica is a real Goldilocks, and this may be one of the reasons why it is so difficult to find in the wild and so difficult to maintain a multi-generational population in the laboratory.
They live in tidal pools that wash away with each tide, but they need currents that are gentle enough to prevent them from being swept out to the open ocean. They like the water to be salty but also a little fresh and prefer an environment where they mingle.
They need the opportunity to bask in the sun to photosynthesize, but they also like to be close to their favorite food source—and, “like your typical four-year-old, they're just extremely picky eaters,” Krug says.
Because they don't have a true skin barrier, they are sensitive to pollution.
Sea slugs are also vulnerable to any changes in currents, so any nearby development that changes the flow of water could displace an entire population. And if they are moved from a particular location, it could be decades before another slug accidentally swims in, perhaps hundreds of kilometers away, and establishes a new population, Stevens says.
“The likelihood of that happening is very, very low,” Stevens says. “Finding more habitat for, say, a little slug that’s just crawling along the ground or just floating in the water column is really an opportunity in the dark.”
Stevens talks about when he learned about Oftenort's discovery V Rainbow Haven Provincial Park: “My eyes nearly popped out of my head.”
He headed there a few days later and says the snorkeling took about 10 minutes before he spotted one small sea slug.
“And right after that it was like, boom, boom, boom.”
Returning to land after another visit to the 6C water on a cold early November morning, Oftenort shouted to the shore that she had just seen “hundreds, if not thousands.”
Since sharing his discovery online, Stevens has attracted researchers. contact him from both the east and west coasts of the United States.
The fact that the recent discovery of this thriving population was made within a provincial park in Nova Scotia underscores how important protected areas are to biodiversity, Stevens says.
“As coastal development spreads and continues to evolve, some of these populations we may not even know about and they will disappear,” he says. “And so as time goes on, these slugs are likely to become increasingly rare.”
Stevens says Oftenort's discovery highlights the importance of citizen science.
“It just shows the power of curiosity and that anyone here can get in the water and still have the potential to find that really scientifically significant observation.”
Oftenort has returned to look at the slugs several times since her discovery.
Her passion for living things is evident in the way she talks about them. If someone can say that Elysia chromotica has a face that only his mother could love, then she calls it “sweet patootie.”
She hopes that by sharing her finds online, others will see the beauty in them too.
“I think the more of us who know what's out there, the more I hope we'll be more enthusiastic about protecting what we have here. It's really special that we have so much ocean in Nova Scotia and so many cool and fascinating creatures out there.”
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