Their arms literally fall off as the disease progresses
Desde 2013, una enfermedad misteriosa arrasó con más de cinco mil millones de estrellas de mar a lo largo de la costa del Pacífico norteamericano, desencadenando un colapso ecológico en cadena que transformó los bosques de kelp en desiertos marinos. Tras más de una década de investigación, científicos del Instituto Hakai han identificado a la bacteria Vibrio pectenicida como la responsable, un hallazgo publicado en Nature Ecology and Evolution que abre por fin una puerta hacia la restauración. La historia de este descubrimiento es también la de la paciencia científica: la verdad estaba oculta en el líquido celómico de los animales infectados, un lugar que nadie había pensado en mirar hasta ahora.
- En cinco años, la estrella de mar girasol perdió el noventa por ciento de su población, y con ella desapareció el principal depredador de los erizos de mar en el Pacífico norte.
- Sin estrellas de mar que los controlaran, los erizos se multiplicaron sin freno y devoraron el noventa y cinco por ciento de los bosques de kelp del norte de California en apenas una década.
- Durante años, los investigadores persiguieron pistas falsas —un densovirus que resultó ser un habitante inofensivo de animales sanos— mientras el verdadero culpable permanecía oculto en muestras que nadie analizaba.
- El giro decisivo llegó cuando el equipo del Instituto Hakai examinó el líquido celómico de los animales infectados y encontró allí a Vibrio pectenicida, la bacteria que había eludido a la ciencia durante más de diez años.
- Con el agente causal identificado, los científicos pueden ahora explorar traslados de poblaciones, programas de cría en cautividad e investigación sobre inmunidad natural para reconstruir ecosistemas enteros que dependen del regreso de estas estrellas.
A partir de 2013, un síndrome de deterioro comenzó a recorrer la costa del Pacífico norteamericano de México a Alaska, matando a más de cinco mil millones de estrellas de mar. La estrella girasol, una de las más abundantes de la región, perdió cerca del noventa por ciento de su población en los primeros cinco años. La enfermedad era perturbadora en su forma de actuar: lesiones que se abrían en el cuerpo del animal hasta que sus brazos, simplemente, se desprendían y caían. Alyssa Gehman, ecóloga de enfermedades en el Instituto Hakai de Columbia Británica, lo describió sin rodeos: «Es realmente bastante horrible».
Durante más de una década, la causa permaneció sin identificar. Las primeras investigaciones apuntaron a un densovirus, pero resultó ser un habitante habitual de animales sanos. Otros equipos analizaron tejidos de animales muertos, pero ignoraron el líquido celómico —el fluido que rodea los órganos internos— donde el verdadero culpable se escondía. Fue el equipo del Instituto Hakai quien, al analizar precisamente ese fluido en animales infectados, encontró a la bacteria Vibrio pectenicida. El hallazgo, publicado esta semana en Nature Ecology and Evolution, fue calificado por el microbiólogo Blake Ushijima, de la Universidad de Carolina del Norte en Wilmington, como «realmente inteligente y significativo».
El descubrimiento importa mucho más allá de las estrellas de mar. Estos animales son depredadores voraces de erizos, y su desaparición desencadenó una reacción en cadena: los erizos se dispararon en número y consumieron el noventa y cinco por ciento de los bosques de kelp del norte de California. Esos bosques —comparados por la investigadora Rebecca Vega Thurber con «las selvas tropicales del océano»— son hogar y sustento de peces, nutrias, focas y decenas de otras especies. Ahora que se conoce el agente causante, los científicos pueden evaluar traslados de poblaciones, programas de cría en cautividad e investigar si algunas estrellas poseen inmunidad natural. Restaurar a estos animales no es salvar una sola especie: es reconstruir un ecosistema del Pacífico que lleva más de una década desmoronándose.
For more than a decade, something was killing sea stars along the Pacific coast of North America. Starting in 2013, a wasting syndrome swept from Mexico to Alaska, leaving behind a trail of devastation so complete that scientists struggled even to name what they were witnessing. By the time researchers began to understand the scope of the catastrophe, more than five billion sea stars were dead. The sunflower sea star, once abundant across the region, had lost roughly ninety percent of its population within the first five years alone.
The disease itself was grotesque in its mechanics. Healthy sea stars—creatures that typically sport five arms, though some species boast as many as twenty-four—display firm, extended limbs in shades of orange, purple, brown, or green. But the wasting syndrome transformed them. Lesions would form across their bodies, and then, quite literally, their arms would detach and fall away. Alyssa Gehman, a disease ecologist at the Hakai Institute in British Columbia who helped crack the case, described the progression with clinical precision: healthy animals have "swollen arms that extend straight out," but the disease causes them to develop wounds before the limbs simply drop off. "It's really quite horrifying," she said.
For years, the cause remained elusive. Researchers chased false leads—early investigations pointed toward a virus, specifically a densovirus that seemed like a plausible culprit. But when scientists examined the densovirus more carefully, they discovered it was simply a normal inhabitant of healthy sea stars, unrelated to the die-off. Other research teams studied tissue samples from dead animals, but those samples lacked the crucial fluid surrounding the organs—the coelomic fluid—where the real killer was hiding. The detective work stretched on, frustrating and inconclusive, until a team led by researchers at the Hakai Institute took a different approach. They analyzed the coelomic fluid itself and found the bacterium responsible: Vibrio pectenicida.
The discovery, published this week in Nature Ecology and Evolution, represents a breakthrough that had eluded the scientific community for more than ten years. Melanie Prentice, a coauthor of the study, explained how earlier investigations had inadvertently missed the pathogen by focusing on the wrong biological samples. Blake Ushijima, a microbiologist at the University of North Carolina at Wilmington who was not involved in the research, praised the work as "really intelligent and significant," noting that tracing the source of environmental diseases—especially underwater—is "incredibly difficult."
Now that the culprit has been identified, intervention becomes possible. Scientists can evaluate which remaining sea stars are healthy and consider whether relocation or captive breeding programs might restore populations to areas that have been nearly emptied of sunflower sea stars. Researchers can also investigate whether some populations possess natural immunity and whether treatments like probiotics might strengthen resistance to the bacterium. But the stakes extend far beyond the sea stars themselves. These animals are voracious predators of sea urchins, and their collapse has triggered a cascade of ecological consequences. With sea stars nearly gone, urchin populations exploded, and those urchins consumed roughly ninety-five percent of the kelp forests in northern California within a decade. Gehman described sea stars as deceptively innocent-looking creatures that "eat almost everything that lives on the ocean floor." Those kelp forests—which Gehman's colleague Rebecca Vega Thurber compares to "the rainforests of the ocean"—provide food and habitat for fish, sea otters, seals, and countless other species. Restoring the sea stars is therefore not a matter of saving one animal, but of rebuilding an entire Pacific ecosystem that has been fundamentally altered by their absence.
Notable Quotes
It's really quite horrifying— Alyssa Gehman, disease ecologist at the Hakai Institute
Sea stars eat almost everything that lives on the ocean floor— Alyssa Gehman, describing the ecological role of sea stars
The Hearth Conversation Another angle on the story
Why did it take so long to find the bacteria? It seems like something scientists should have discovered quickly.
They were looking in the wrong places, literally. Early teams examined tissue samples from dead sea stars, but the bacteria lives in the fluid around the organs—the coelomic fluid. Once they died, that fluid was gone. It's like searching a crime scene after the evidence has been cleaned up.
So the sunflower sea star lost ninety percent of its population. That's almost complete extinction. Why does that matter beyond the sea stars themselves?
Because sea stars eat sea urchins. A lot of them. When the stars disappeared, urchin populations exploded and ate ninety-five percent of the kelp forests in northern California. Those forests are the foundation of the entire ecosystem—fish, otters, seals, everything depends on them.
And now that they know it's a bacterium, what can they actually do?
They can try to breed healthy sea stars in captivity and reintroduce them. They can look for populations that might have natural immunity. They might even use probiotics to strengthen resistance. But it's delicate work—you can't just restore the predators without thinking about what happens to the prey.
What do you mean?
Once the sea stars recover, they'll start eating urchins again. That's good for the kelp. But if you're not careful about where and how many you release, you could create new imbalances. It's not just about bringing back one species—it's about rebuilding an entire system.