Uno scuticociliato unicellulare è stato identificato come la causa di una moria di massa nel 2022 di ricci di mare a lungo raggio nei Caraibi e lungo la costa orientale della Florida. Questi ricci sono fondamentali per la salute delle barriere coralline e la scoperta solleva interrogativi sull’esistenza del ciliato, sulle condizioni di crescita e sul potenziale impatto su altri organismi. Foto del riccio di mare dalle lunghe spine (Diadema antellarum).
La moria di massa del riccio di mare dalle lunghe spine – che minaccia la salute delle barriere coralline dalle isole caraibiche alla costa orientale della Florida – è stata causata da un organismo unicellulare chiamato ciliato.
La ricerca del killer del 2022 che ha decimato le popolazioni di ricci di mare lungo le isole dei Caraibi e la costa orientale della Florida è terminata. Un team di ricercatori guidato da Mia Breitbart, Distinguished University Professor presso il College of Marine Sciences della University of South Florida, ha identificato un organismo unicellulare chiamato ciliato nella moria di massa di un animale marino importante per le barriere coralline. Salute.
I loro risultati sono stati riportati sulla rivista il 19 aprile 
Ciliate culture viewed under the microscope. Credit: Mya Breitbart USF College of Marine Science
“We’re beyond thrilled to get to the bottom of the 2022 mystery and a bit stunned we did it so quickly,” said Breitbart, senior author on the Science Advances study and an expert in marine genomics. “We had a great team in place and the tools needed to do the ocean science equivalent of a forensic investigation.”
Ciliates are microscopic organisms covered in hair-like structures called cilia that help them move and eat. They are found almost anywhere there is water and most are not disease-causing agents. However, this specific species of ciliate – called a scuticociliate – has been implicated in die-offs of other marine species, such as sharks, in the past.
Photo compilation showing the same sea urchin before and after infection with the ciliate in the USF aquarium research facility. Credit: Makenzie Kerr USF College of Marine Science
Examining urchins collected from 23 sites in the Caribbean, the research team used a series of techniques to confirm the source of the die-off event.
After identifying the ciliate in every affected urchin specimen using genomic techniques, the team grew ciliates in the lab and performed infection experiments at the USF College of Marine Science. When the pathogen was introduced to otherwise healthy urchins in an aquarium tank, the urchins died within a few days – replicating what was taking place in the ocean and confirming the ciliate as the disease source.
DaSc-affected sea urchin, Aruba, August 2022. Credit: Ian Hewson Cornell University
“We’re excited to share this information with everyone, from reef managers to additional scientists so we can explore it further and try to stop its spread,” Breitbart said.
Mya Breitbart (USF) viewing the ciliate culture by microscopy. Credit: Makenzie Kerr USF College of Marine Science
The long-spined sea urchins inhabit shallow tropical waters and feed on algae that would otherwise destroy a reef. They began to lose their spines within days of contracting an unknown disease and died in droves starting in January 2022.
A similar die-off event took place in the early 1980s, which wiped out 98 percent of the long-spined sea urchin population. The culprit of that die-off remains a mystery.
Breitbart first got the call about the unfolding die-off at the end of March 2022. She immediately assembled a team consisting of Ian Hewson, lead author on the publication and a marine ecologist at Cornell University; Christina Kellogg, a microbiologist from the U.S. Geological Survey in St. Petersburg, Fla. who has worked extensively on coral reef diseases; and USF graduate student Isabella Ritchie.
“At the time, we didn’t know if this die-off was caused by pollution, stress, something else – we just didn’t know,” said Hewson, an expert in diseases that cause mass die-offs of sea stars, who flew from New York to the Caribbean Islands to observe the situation.
Even with the source of the mysterious die-off uncovered, questions still remain. For example:
- Is this ciliate new to the area, or was it there prior to the die-off?
- If it has been there, what environmental conditions favored its growth and why did it infect the urchins?
- Can it affect other species of urchins?
“Una teoria che abbiamo è che il ciliato è cresciuto meglio in condizioni di alta produttività, che è ciò che è stato visto nei Caraibi quando ha iniziato a morire”, ha detto Kellogg. “Siamo anche interessati al fatto che questa mortalità si sia verificata in alcune aree geografiche e che le barriere coralline stiano diminuendo a causa della malattia da perdita del tessuto del corallo pietroso”.
Nota: Ian Hewson, Isabella D. Richie, James S. Evans, Ashley Altera, Donald Behringer, Erin Bowman, Marilyn Brandt, Kayla A. Butt, Rulio A Camacho, Thomas O. Cornwell, Peter D. Countway, Aldo Kroeger, Gabriel A. Thine, Christopher Territo, Elizabeth Duermidt-Morey, Ruth Frances-Floyd, Samuel Gittens, Leslie Henderson, Alvin Hilkema, Christina A. GillockYas Kimani A. Kitson-Walters, Patricia Kramer, Judith C. Long, Harilas Lesios, Lauren Liddy, David Marancik, Stephen Nimrod, Joshua D. Patterson, Marit Bister, Isabelle C. Rosemary, Rita Cellarez-Blasco, Moriah LB Seyam, Moriah LB Seyam C. Sharp, Matthew Souza, Andrea Valdez-Trinidad, Marijn van der Laan, Brian Villanova-Guez, Maria Villalbando, Sarah D. Van Hoyne, Matthew Warham, Tom Vigers, Stacey M. Williams, Thierry M. Lavoro, Roy B. Yanong, Somira Zambrano, Alizy Zimmerman, Mia Breitbart, 19 aprile 2023, Progressi scientifici.
DOI: 10.1126/sciadv.adg3200
Questa ricerca è stata finanziata dalla National Science Foundation, un Atkinson Center for a Sustainable Future Rapid Response Award, AGGRA, National Oceanic and Atmospheric Administration, National Fish and Wildlife Foundation, Florida Keys Marine Sanctuary e Florida Fish and Wildlife Conservation Commissione.
