A USF professor discovered what was killing sea urchins in Florida, Caribbean. Here’s how.

ST. PETERSBURG — She called it cute, the microscopic single-celled organism on her microscope slide. She said she liked its little hairs, and the way it swam beneath her lens. Looking through her microscope, Mya Breitbart found one of the ciliates — this type of single-celled creature — and smiled.

But what could make this ciliate famous is not cute at all.

Beginning in January 2022, divers began to see a species of long-spined sea urchins, known as Diadema antillarum, dying in droves, spanning from the Caribbean to the Florida Keys. Something was infecting them, causing their spines to literally fall off their bodies. But it wasn’t quite clear what it was.

In many cases of disease spread, it is difficult to determine the cause with certainty, Breitbart, a professor of biological oceanography at the University of South Florida’s College of Marine Science, said. There was a similar large-scale urchin die-off in the 1980s that killed 98% of the species, but no one ever found the offender. Urchin populations were still recovering from that event when this infection struck, Breitbart said.

And now, after only four months of research on the 2022 deaths — an unusually quick time frame — Breitbart and her team have proved the “cute” ciliate, formally called Philaster apodigitiformis, but frequently referred to as Philaster, was the culprit.

“Science never works like this,” Breitbart said.

The discovery was announced in an article Wednesday in the journal Science Advances. Two days before the release, Breitbart gave the Tampa Bay Times a tour of her St. Petersburg lab and explained her team’s findings.

Breitbart’s specialty is researching creatures far too small for our eyes to see. She has miniature microscopes in her office — and a few more at home. Pictures of sea creatures line her office walls, as well as artwork of the small cells she studies. In fact, the micrometer-sized Philaster actually qualifies as big for her, Breitbart said.

The first stop on the tour was Breitbart’s microscope room. On a day that wasn’t so comfortable to her — with a camera pointed at her and rounds of interviews about her work to come — she sought the familiarity of her seat in front of the lens. Her microscope slide was already prepared, and a video of the pathogen swimming around was already playing on an HP desktop monitor.

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“I’m happy at the microscope,” Breitbart said with a grin.

Breitbart began to talk about how cool she thought one little drop of solution on her slide was. She focused her microscope on just one Philaster, but there were hundreds to be found.

She described how she’s watched the pathogen multiply on slides before — by simply splitting from one cell into two. She said as long as Philaster have food — urchins being among their favorite foods — they can multiply and continue to invade and infect.

In the wild, that one drop could be responsible for killing dozens of urchins, she said.

“That’s insane — I don’t know a better way of saying that,” Breitbart said.

Breitbart’s next stop was another lab one door down the hallway. That’s where her cultures of Philaster live. They live in test tubes, thousands of them in each vial. There is one grain of rice in each tube, which Breitbart said is covered in bacteria to feed the ciliates.

In her lab, she continues to breed the ciliates for study in a meticulous, organized method. Standing next to her Philaster farm, Breitbart leaned on the black counter and began to tell her story.

Breitbart received a call from a colleague in March 2022 asking if she wanted to study what might be killing the urchins. Breitbart had never worked with urchins before, but she said whenever someone asks her if she wants to research something, she’ll probably say yes.

“As soon as I knew it was Diadema, I was like, ‘Yes, we have to figure this out’ — because in that ’80s die-out, just the loss of this one species of urchin completely changed the fate of coral reefs,” Breitbart said.

But what she and her team were looking for was completely unclear, she said. When Breitbart’s lab received its first set of urchin samples, she said they checked for a wide range of possible causes, including whether it was a virus or a bacteria — even for hand sanitizer in urchins found dead near cruise ship docks.

Breitbart’s team found the ciliate present in sick urchins’ muscle tissue. The healthy urchin samples did not have Philaster.

This type of ciliate is a known pathogen, Breitbart said, so it immediately raised a red flag as a possible cause. The next step was to prove it.

To do this, Breitbart had to show that Philaster can transmit disease to otherwise healthy urchins. In July 2022, Breitbart and her team put just 20 Philaster into a controlled tank with healthy urchins. Within a few days, the urchins showed the exact same symptoms as the sick urchins in the ocean: Their spines fell off, their tube feet lost their suction ability and they looked increasingly weaker until they died.

Simultaneously, in a neighboring building to Breitbart’s lab, the Florida Fish and Wildlife Commission performed tests on the same samples and found the same result: the presence of Philaster in the sick sea urchins. With two experiments pointing to the Philaster, Breitbart could confirm this was the cause of the mass deaths.

“It’s definitely an ‘aha!’ moment — or more of an ‘oh my God’ moment,” Breitbart said. “All of us on our team have been working on marine diseases for a long time, and this just doesn’t happen. This is really unprecedented to figure it out.”

There aren’t samples from the 1980s outbreak to test, Breitbart said, so it’s not known if the same organism also was responsible for the deaths of those urchins. It might take a DeLorean to answer that question.

Having proved it as the cause of the deaths, Breitbart began to grow her Philaster farm to continue her testing. The cells are not dangerous to humans, Breitbart said.

But the discovery of the urchins’ cause of death left the team with many more questions they hope to answer in the future. Breitbart said there are very long text message threads with her teammates of additional questions to research.

There is no way to protect the long-spined sea urchins at this point. Breitbart said they’ve found a chemical that can kill the ciliate, but there likely would be negative impacts from just dumping the chemical into the wild.

That research will continue in Breitbart’s lab.

Wrapping up the story of her discovery, Breitbart walked back to her office and sat at her table, with the Science Advances article printed out next to her. There’s a smile on her face as she thinks back on her work. She said she’s proud of the discovery and called it a career highlight.

She said she also is relieved to have the results of her research made public so she can discuss it with other scientists and more minds can be added to help answer the team’s remaining questions. They’ve had this answer since July of last year, and Breitbart said she is ready to do more than just go home at night and think “I think we’ve got it,” over and over.

“I never thought I would be able to solve a mystery like this in my career,” Breitbart said. “We so rarely actually figure out the cause. So just being a part of that was really incredible. I still often am like, ‘I can’t believe we figured that out,’ or ‘I can’t believe we figured that out so quickly.’”