The anacondas are a mirror of what the water has become.
En las aguas de la Amazonía ecuatoriana, un equipo de científicos descubrió en 2022 que lo que durante décadas se creyó una sola especie —la anaconda verde— es en realidad dos linajes separados hace diez millones de años. Más allá de reescribir la taxonomía, el hallazgo convirtió a estas serpientes en testigos vivos de una crisis ambiental: los machos acumulan metales pesados a niveles que reflejan, con inquietante fidelidad, la exposición de las comunidades amazónicas a los tóxicos del petróleo. La naturaleza, una vez más, nos habla de nosotros mismos.
- Lo que parecía una especie única resultó ser dos linajes con una diferencia genética del 5,5 %, mayor que la que separa a humanos y simios, obligando a reescribir décadas de certeza taxonómica.
- Los machos de la nueva especie, Eunectes akayima, acumulan cadmio y plomo en concentraciones más de diez veces superiores a las de las hembras, una señal de alarma imposible de ignorar.
- La causa está en la dieta: mientras las hembras cazan presas terrestres, los machos consumen peces depredadores y caimanes que ya cargan con los tóxicos de ríos y sedimentos contaminados por derrames petroleros.
- Esa misma dieta acuática es la base alimentaria de miles de personas amazónicas, lo que convierte a los anacondas macho en indicadores biológicos del riesgo que enfrentan las comunidades que comparten su hábitat y su mesa.
En 2022, un equipo de científicos recorrió las aguas del territorio Baihuaeri Waorani en Ecuador acompañado de guías indígenas, en busca de anacondas verdes. Lo que encontraron —y lo que National Geographic registró para su docuserie Pole to Pole— fue una hembra de casi cinco metros sostenida por manos waorani mientras el toxicólogo Bryan Fry tomaba muestras de escamas. Esas muestras terminarían por desmantelar décadas de certeza científica.
El análisis genético reveló que la anaconda verde, clasificada durante años como Eunectes murinus, es en realidad dos especies distintas que divergieron hace aproximadamente diez millones de años. La recién identificada Eunectes akayima —la anaconda verde del norte— habita la cuenca amazónica al norte de los grandes ríos, desde Ecuador hasta las Guayanas. Su prima sureña, la E. murinus original, se distribuye por Brasil, Perú y Bolivia. La distancia genética entre ambas, un 5,5 % de su ADN total, supera la que existe entre humanos y simios.
Pero el hallazgo más perturbador no vino de la genética, sino de lo que los cuerpos de los anacondas revelaban sobre su entorno. Fry detectó que los machos acumulaban cadmio y plomo —metales pesados propios de los derrames petroleros y potentes disruptores endocrinos— en concentraciones más de diez veces superiores a las de las hembras. La explicación está en la ecología: las hembras, más grandes, cazan presas terrestres como venados; los machos, más ágiles, persiguen peces depredadores y caimanes que ya han concentrado toxinas de aguas y sedimentos contaminados.
Esa diferencia dietética convierte a los machos en archivos vivientes de la contaminación acuática. Y la implicación para las personas es directa: las comunidades amazónicas comparten esa misma dieta de peces y animales acuáticos. Lo que los anacondas acumulan en sus tejidos es, en esencia, un espejo de lo que acumulan quienes viven y se alimentan en los mismos ríos.
In 2022, a team of scientists and guides navigated the murky waters of the Baihuaeri Waorani territory in Ecuador's Amazon, searching for green anacondas in their natural habitat. What they found—and what National Geographic would later film for its docuseries Pole to Pole with Will Smith—was a female anaconda stretching nearly five meters long, her body held steady by indigenous Waorani guides while toxicologist Bryan Fry collected scale samples for genetic analysis. The footage captures a moment of scientific routine that would eventually upend decades of taxonomic certainty: the green anaconda, long assumed to be a single species, was actually two.
The genetic samples collected that day revealed the split. What scientists had classified for years as Eunectes murinus—the green anaconda—turned out to be two distinct species that had diverged roughly ten million years ago. The newly identified northern species, Eunectes akayima, inhabits the Amazon basin north of the river systems, spanning Ecuador, Colombia, Venezuela, and the Guianas. Its southern cousin, the original E. murinus, lives south of the main channel, ranging across Brazil, Peru, and Bolivia. The genetic distance between them—5.5 percent of their total DNA—exceeds the genetic difference between humans and apes, a fact that underscores how profoundly these populations have drifted apart over the millennia.
But the discovery's most striking revelation emerged not from the genetics themselves, but from what the anacondas' bodies were telling researchers about their environment. Fry, a professor at the University of Queensland, noticed something alarming in the tissue samples: the male anacondas carried vastly different contamination loads than the females. The difference was not marginal. Cadmium and lead—heavy metals characteristic of oil spills and potent endocrine disruptors—appeared in male anacondas at concentrations more than ten times higher than in females. The reason lay in ecology and diet.
Female northern green anacondas, larger and heavier than males, hunt in the lower reaches of the food chain, taking deer and other terrestrial prey. Males, by contrast, are sleeker and more agile, pursuing predatory fish and caimans—apex aquatic hunters that themselves accumulate toxins from contaminated water and sediment. By consuming these predators, male anacondas become repositories for environmental poisons, their bodies a living record of pollution levels in the rivers and wetlands they inhabit. The sexual dimorphism that allows these snakes to partition their ecological niche—to hunt different prey and occupy different positions in the food web—also makes males sensitive indicators of aquatic contamination.
Fry's observation carries a sobering implication for human populations in the Amazon. The diet of male anacondas mirrors that of many Amazonian people: fish and aquatic animals form a dietary staple. If male anacondas are accumulating heavy metals at such extreme concentrations, the people who share their habitat and their food sources are likely doing the same. The contamination is not a subtle signal. It is a biological alarm, written in the tissues of snakes that have lived in these waters for millennia, now bearing witness to the chemical legacy of oil extraction and industrial activity. What the anacondas reveal about their environment is, in essence, what they reveal about the people who live there too.
Notable Quotes
Finding a new species often isn't about active searching, but about having a rigorous scientific process so that chance can emerge.— Bryan Fry, toxicologist at University of Queensland
The concentrations of cadmium and lead in males were more than 1,000% higher than in females. It's not a subtle difference. It's a warning signal.— Bryan Fry
The Hearth Conversation Another angle on the story
Why does it matter that these are two species instead of one?
Because it tells us the anacondas have been living separate lives for ten million years. They've accumulated enough genetic distance that they're genuinely different animals now. But more importantly, it forced scientists to look closer at what those differences actually mean—and that's when the contamination story emerged.
So the males and females being different sizes—that's not unusual for snakes, is it?
It's not unusual, but the degree matters here. The females are massive, the heaviest snakes on Earth. The males are built lean. That size difference isn't cosmetic. It determines what they can hunt, where they hunt, what they eat. It partitions their world.
And that's why the males are so contaminated?
Exactly. They're eating predatory fish and caimans that live in the water column, where the oil and heavy metals settle. The females hunt on land or in shallower areas. The males are essentially bioaccumulating everything the water has absorbed.
But why does that matter for humans?
Because Amazonian people eat the same things the male anacondas eat. Fish, caimans. If the snakes are carrying ten times the contamination, the people probably are too. The anacondas are a mirror.
Is anyone measuring contamination in the people?
The source doesn't say. But Fry's point is that the anacondas are doing the measuring for us. Their bodies are the data. The question now is whether anyone acts on what the data shows.
What happens next?
That depends on whether governments and oil companies take the signal seriously. Right now, the anacondas are speaking. The question is whether anyone is listening.