Oamenii de știință demasc amenințarea microscopică din spatele unui eveniment mortal masiv
Un scuticociliat, un organism unicelular, a fost identificat drept cauza morții în 2022 a aricilor de mare cu țepi lungi în Caraibe și pe coasta de est a Floridei. Acești arici de mare sunt esențiali pentru sănătatea recifelor de corali, iar descoperirea ridică întrebări cu privire la prezența ciliatelor, condițiile de creștere și impactul potențial asupra altor specii. Fotografie cu arici de mare cu spin lung (Diadema antillarum).
Moartea în masă a aricilor de mare – o pierdere care amenință sănătatea recifelor de corali din Caraibe până pe coasta de est a Floridei – a fost cauzată de un organism unicelular numit ciliat.
Căutarea ucigașului din 2022 care a decimat populația de arici de mare din Caraibe și de-a lungul coastei de est a Floridei s-a încheiat. O echipă de cercetători organizată de Mya Breitbart, profesor emerit la Colegiul de Științe Marine din cadrul Universității din Florida de Sud, a identificat un organism unicelular numit ciliat drept cauza unui eveniment de mortalitate în masă la un animal marin vital pentru recifele de corali. . sănătate.
Descoperirile lor au fost raportate pe 19 aprilie în jurnal 
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?
„O teorie pe care o avem este că ciliatul a crescut bine în condiții de productivitate ridicată, care au fost observate în Caraibe când a început mortalitatea”, a spus Kellogg. „Suntem, de asemenea, curioși că există o suprapunere în anumite zone geografice în care a avut loc această mortalitate și unde coralii sunt în scădere din cauza bolii pierderii țesutului coralilor pietroși.”
Referință: „Scuticociliate causes mass mortality of Diadema antillarum in the Caribbean Sea” de Ian Hewson, Isabella T. Ritchie, James S. Evans, Ashley Altera, Donald Behringer, Erin Bowman, Marilyn Brandt, Kayla A. Budd, Ruleo A. Camacho , Tomas O. Cornwell, Peter D. Countway, Aldo Croquer, Gabriel A. Delgado, Christopher DeRito, Elizabeth Duermit-Moreau, Ruth Francis-Floyd, Samuel Gittens, Leslie Henderson, Alwin Hylkema, Christina A. Kellogg, Yasunari Kiryu, Kimani A. Kitson-Walters, Patricia Kramer, Judith C. Lang, Harilaos Lessios, Lauren Liddy, David Marancik, Stephen Nimrod, Joshua T. Patterson, Marit Pistor, Isabel C. Romero, Rita Sellares-Blasco, Moriah LB Sevier, William C Sharp, Matthew Souza, Andreina Valdez-Trinidad, Marijn van der Laan, Brayan Vilanova-Cuevas, Maria Villalpando, Sarah D. Von Hoene, Matthew Warham, Tom Wijers, Stacey M. Williams, Thierry M. Work, Roy P. Yanong , Someira Zambrano, Alizee Zimmermann, Mya Breitbart, 19 aprilie 2023, Oamenii de știință progresează.
DOI: 10.1126/sciadv.adg3200
Cercetarea a fost finanțată de Fundația Națională pentru Știință, Atkinson Center for Sustainable Futures Rapid Response Award, AGGRA, National Oceanic and Atmospheric Administration, National Fish and Wildlife Foundation, Florida Keys Marine Sanctuary și Florida Fish and Wildlife Preservation Commission.