A rare photosynthesizing sea slug has been found in NS, which is why scientists are excited

When he made the discovery that would thrill his fellow snorkellers and excite researchers across North America, he didn’t think much of it at first.

“I just thought, ‘Oh, it’s a rotten leaf, keep going,'” says Ellie Ofthenorth.

The avid snorkeller passed by this “black gunk” once, twice, but it wasn’t until the third pass that something caught her eye up close and she realized it was a living creature.

“I just started yelling, there’s a sea slug in here!”

Ofthenorth’s mother, who was on the shore of Rainbow Haven Provincial Park near Dartmouth, NS, turned on the snorkel group chat and within minutes members had identified it as Alicia chlorotica, or Eastern Emerald Alicia.

This simple creature might be almost as good as your garden-variety slug—the kind that destroys your lettuce every summer. That is, until his shriveled-looking back reveals a stunning, emerald green “leaf” filled with yellow “veins” radiating outward from the center.

This “leaf” and what it does to the sea slug has lots of potential for research. Medical, clean energy and other fields.

But it is so elusive that researchers are having difficulty studying it.

Alicia chlorotica can photosynthesize by eating algae, stealing their chloroplasts – the organelles that perform photosynthesis, keeping them alive in its body, and using them to capture energy from the Sun. Sea slugs can survive for several months without consuming food.

“It’s like I ate a whole bunch of spinach and then I woke up this morning and just sunbathed for an hour and then I wouldn’t need to eat all week,” says Hunter Stevens, a biologist with the Nova Scotia chapter of the Canadian Parks and Wilderness Society. “These slugs are basically doing the same thing.”

While the ability to photosynthesize is rare in the animal kingdom, Alicia chlorotica is not unique in this regard. Other sea slugs can do this too, but none as good as Elysia chlorotica.

“Elysia chlorotica is kind of the reigning world champion,” says Patrick Krug, a professor of biological sciences at Cal State University, Los Angeles, who studies marine invertebrates. For decades.

Krug says researchers don’t know how long Alicia chlorotica can go without eating.

He says other species he has worked on in the lab gradually become “bleached” and unable to keep chloroplasts alive.

“Chlorotica simply doesn’t,” says Krug. “I kept them in my laboratory once and I never saw them turn green. For all the months I kept them, they were just as green, just surviving on light, and they never turned green.”

Potential Research Applications

Researchers want to find out how Elysia chlorotica accomplishes this feat so well, and hope that uncovering its secrets may eventually help humans.

Scientists say these insights may someday lead to advances in wound repair, energy and nutrient supplementation, drug treatments, clean energy technology and biophotovoltaic cells.

Joshua Widalm is associate professor of horticulture and director of the Purdue Center for Plant Biology in Indiana. For the past six years, he has been studying a different species of photosynthesizing sea slug – Alicia crispata, commonly known as the lettuce sea slug – because Alicia chlorotica is so difficult to find and maintain.

He says uncovering the mystery of how these organisms steal chloroplasts, incorporate them into their cells and keep them functional could have implications for everything from vaccines to chemotherapeutic drugs, herbicides or pesticides, which are expensive to synthesize.

Additionally, since the process of photosynthesis produces oxygen, understanding how sea slugs protect themselves or get rid of excess oxygen could advance research on human inflammatory diseases, neurodegenerative diseases, cancer or even age-related conditions, Widalm says.

“The only limit is the imagination,” he says.

elusive and fleeting

However, this iconic slug is excellent at evading researchers.

Historically, known populations have existed in the Minas Basin region of Nova Scotia and Martha’s Vineyard in Massachusetts – and theoretically their habitat exists on the eastern seaboard of the US – but recent efforts to locate them have been unsuccessful.

“For so long it seemed as if no one had seen them,” says Krug. “It was such a shot in the dark that it wasn’t even worth seeing.”

Dylan Gagler, a PhD student at the American Museum of Natural History in New York, has repeatedly searched for the slug’s preferred habitat near Martha’s Vineyard this year, but so far without success.

When Stevens’ Instagram post about discovering Rainbow Haven appeared in Gaggler’s feed, he said he was having “like a crazy, FOMO (fear of missing out) moment, like, I have to go up to Nova Scotia. Like, this is obviously where all the action is.”

Gagler contacted Stevens to obtain information about the conditions at the Rainbow Haven location, such as air and water temperatures and the depth at which they were found, in order to improve his discoveries. He is also exploring the permitting process to collect samples from Nova Scotia to scale up in the laboratory.

Although Alicia chlorotica is hard to find, Krug says there have been a few sightings in recent months, including in Nova Scotia as well as the Carolinas and Tampa Bay, Florida.

He says the population is “transient”, appearing to go through boom and bust cycles – sometimes being abundant, but then suddenly disappearing.

Requires specific housing, food

Alicia chlorotica is the ultimate Goldilocks – and that may be why it is so hard to find in the wild and so difficult to maintain multi-generational populations in a laboratory.

They live in tidal ponds that drain with each tide, but they need currents that are gentle enough so that they will not be swept out into the open ocean. They like water salty, but also a little fresh, and prefer an environment where there is a mix of both.

They need to be able to be in sunlight for photosynthesis, but they also like to be close to their favorite food source—and, “like your typical four-year-old, they’re very finicky eaters,” says Krug.

Because they lack a true skin barrier, they are sensitive to pollution.

Sea slugs are also sensitive to any changes in currents, so any nearby development that alters the flow of water can displace entire populations. And if they are displaced from a particular location, it could take decades for another slug to establish a new population by chance, perhaps from hundreds of kilometers away, says Stevens.

“The chances of that happening are very, very low,” says Stevens. “Finding as much habitat as a small slug that simply crawls on the ground or that swims through the water column is really a shot in the dark.”

Stevens says that when he learned of Ofthenorth’s discovery In Rainbow Haven Provincial Park, “My eyes almost came out of my head.”

He went there a few days later, and says it took about 10 minutes of snorkeling before he saw a tiny sea slug.

“And then right after that it was like, boom, boom, boom.”

Swimming back to land after encountering 6 °C water on a cold morning in early November, Ofthenorth shouted to the shore that he had just seen “hundreds, if not thousands” of birds.

Since sharing the discovery online, Stevens has researchers Contact him from both the East and West Coast of the US

Stevens says the fact that the recent discovery of this thriving population was made within the boundaries of a provincial park in Nova Scotia underscores how important protected areas are to biodiversity.

“As coastal development continues to grow and move forward, some of these populations we may not even know about will disappear,” he says. “And so these slugs will likely become rarer as time goes on.”

Stevens says Ofthenorth’s discovery highlights the importance of citizen science.

“It just shows the power of curiosity and how anyone here can go into the water and still have the ability to find this scientifically important observation.”

Ofthenorth has already gone back to see the slugs twice since his discovery.

His passion for living beings is evident in the way he talks about them. While some might say that Alicia Chlorotica has a face only her mother could love, she refers to it as her “sweetie patootie.”

She hopes that by sharing her discoveries online others will see the beauty in them.

“I think the more of us we know about what’s out there, my hope is that we’ll be more excited to protect what we have. It’s really special that we have so much ocean in Nova Scotia and so many cool and fascinating creatures beneath it.”

more top stories