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Los científicos revelan la amenaza microscópica detrás de un evento de muerte masiva

Los científicos revelan la amenaza microscópica detrás de un evento de muerte masiva

Un organismo unicelular, escuticociliado, ha sido identificado como la causa de la muerte masiva de erizos de mar de espinas largas en 2022 en el Caribe y la costa este de Florida. Estos erizos son esenciales para la salud de los arrecifes de coral, y el descubrimiento plantea dudas sobre la presencia de ciliados, sus condiciones de crecimiento y su posible impacto en otras especies. Fotografía del erizo de mar largo y espinoso (Diadema antillarum).

La muerte masiva del erizo de mar de espinas largas, una pérdida que amenaza la salud de los arrecifes de coral desde el Caribe hasta la costa este de Florida, fue causada por un organismo unicelular llamado ciliado.

La búsqueda de un asesino terminó en 2022 y acabó con los erizos de mar de espinas largas en el Caribe y a lo largo de la costa este de Florida. Un equipo de investigadores organizado por Mia Breitbart, profesora universitaria distinguida en la Facultad de Ciencias Marinas de la Universidad del Sur de Florida, identificó un organismo unicelular llamado ciliar como la causa de la muerte masiva de un animal marino vital para la salud de los arrecifes de coral.

Sus hallazgos se publican el 19 de abril en la revista Nature. Ciliate Culture Under Microscope

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.

Sea Urchin Before and After Infection

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

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

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 teoría que tenemos es que el ciliado creció bien bajo las condiciones de alta productividad observadas en el Caribe cuando comenzó a desvanecerse», dijo Kellogg. «También tenemos curiosidad por el hecho de que hay cierta superposición en algunas de las áreas geográficas donde ocurrió esta extinción y donde los arrecifes de coral están disminuyendo debido a la enfermedad de pérdida de tejido de coral pétreo».

Referencia: “El agente escuticocilato causa mortalidad masiva de Diadema Antillarum en el Mar Caribe” por Ian Hewson, Isabella T Ritchie, James S Evans, Ashley Alterra, Donald Berenger, Irene Bowman, Marilyn Brandt, Kayla A. Budd y Rolio A. Camacho, Thomas O. Cornwell, Peter D. 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 Sharp, Matthew Souza, Andrina Valdez-Trinidad, Maren van der Laan, Brian Villanova-Cuevas, Maria Villalpando, Sarah de Von Huene, Matthew Warham, Tom Weyers, Stacy M. Yanong, Soumira Zambrano, Alise Zimmerman, Mia Breitbart 19 de abril de 2023 Disponible aquí. Avances de la ciencia.
DOI: 10.1126/sciadv.adg3200

La investigación fue financiada por la Fundación Nacional de Ciencias, el Centro de Respuesta Rápida Atkinson para Futuros Sostenibles, AGGRA, la Administración Nacional Oceánica y Atmosférica, la Fundación Nacional de Pesca y Vida Silvestre, la Reserva Marina de los Cayos de Florida y la Comisión de Pesca y Vida Silvestre de Florida.

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