homehome Home chatchat Notifications


This is the first animal we know that doesn't breathe

We though all life needs oxygen. We were wrong.

Mihai Andrei
February 25, 2020 @ 1:23 pm

share Share

A parasitic creature (distant cousin of the jellyfish) doesn’t have a mitochondrial genome — making it the first multicellular creature we know of that doesn’t need oxygen to survive.

The unseemly parasite features a weird and unique adaptation. Image credits: Stephen Atkinson.

Life is incredibly diverse. From the plant-like corals to the giant mammals and slithering lizards that inhabit the Earth, we’ve found a dazzling variety of creatures. But for all this variety, some things remained unchanged. All life as we know it needs water to survive. It’s all based on carbon — except for some experiments carried out in a lab — and it all needs oxygen. Or so we thought.

The common salmon parasite called Henneguya salminicola is well known to researchers. It causes white cysts that resemble tapioca in the fish muscles, which is why it is also called tapioca disease.

The parasite is a cnidarian belonging to the same phylum as corals, jellyfish and anemones — but it is a distant relative of jellyfish. Henneguya salminicola lives deep inside the fish for its entire lifecycle, which makes for some oxygen-poor conditions.

Researchers have suspected that it must have a special adaptation to allow it to survive when oxygen is scarce, but it wasn’t until Dayana Yahalomi of Tel Aviv University and her colleagues had a thorough look at it that they realized just how weird this adaptation is.

They used deep sequencing and fluorescence microscopy to analyze the parasitic creature, finding that it has completely lost its mitochondrial genome, as well as the capacity for aerobic respiration. Simply put, the creature can’t breathe oxygen.

“Our discovery shows that aerobic respiration, one of the most important metabolic pathways, is not ubiquitous among animals,” the study reads.

Life without oxygen

No oxygen? No problem. At least, if you’re a weird cnidarian parasite infecting salmon. Image credits: Stephen Atkinson.

This is the first macroscopic creature known to not breathe oxygen. This simple trait has been with macroscopic life as we know it, ever since an Archaea swallowed a smaller bacterium, and somehow this worked out for both parties and the two stayed together. That is, the smaller bacteria became an organelle called mitochondria (the fabled powerhouse of the cell), an essential part of the breathing process.

Every cell in your body — and most bodies for that matter — contains large numbers of mitochondria. They break down oxygen to produce a molecule called adenosine triphosphate (ATP), which is then used to power cellular processes. Hence, the powerhouse of the cell thing.

Creatures that live in low-oxygen environments have special adaptations that enable them to survive, but no creature has been observed to completely lack this system.

This raises a number of intriguing questions. For starters where does it get its ATP from? A yet-untested theory is that they somehow leech it from the host, but this is yet to be confirmed. Secondly, how and why did the creature lose its mitochondria?

Researchers suspect that this is a case of genetic simplification, where the parasite simply shed unnecessary, cumbersome DNA as it evolved. This is consistent with the overall evolutionary trend observed in H. salminicola, devolving from a jellyfish-type creature to a much simpler parasite. But the fact that it just shed its mitochondria and ATP synthesis is extreme and very unusual.

Some single-celled creatures have developed mitochondria-type organelles for anaerobic metabolism. But never had this been identified in a multicellular creature — and even whether it was possible at all was debated.

The acquisition of mitochondria was a key step in the evolution of life on Earth. This is a possibility to study life as we didn’t know it before and understand how breathing really works. It’s also a nod that life can sometimes shift in different unexpected directions.

“Our discovery confirms that adaptation to an anaerobic environment is not unique to single-celled eukaryotes, but has also evolved in a multicellular, parasitic animal. Hence, H. salminicola provides an opportunity for understanding the evolutionary transition from an aerobic to an exclusive anaerobic metabolism,” the study concludes.

The study has been published in PNAS.

share Share

Scientists Use Math to Show New Type of Particles Once Considered Impossible Might Be Real

Researchers uncover new particle behaviors that break the two-type mold of quantum mechanics.

Hobbyist Builds AI-Assisted Rifle Robot Using ChatGPT: "We're under attack from the front left and front right. Respond accordingly"

The viral video sparked ethical debates about the broader implications of AI weapons.

Drones Helps Researchers Uncover a Lost Mega-Fortress in Georgia

Researchers have long known about the formidable scale of the Dmanisis Gora fortress, but a recent study has unveiled its true magnitude. Using drone-based imagery and photogrammetry, a team of scientists has revealed that this 3,000-year-old structure in the Caucasus Mountains spans an astonishing 60 to 80 hectares. A cultural crossroads The South Caucasus is […]

Eating more peanuts, herbs, and spices can boost your gut microbiome

A small change in diets can make a big difference for your health.

Did your rent just surge? Blame this price-fixing AI landlord costing Americans $3.6 billion annually

AI is changing the housing market and renters are paying the price.

Melting Antarctic Ice Could Awaken 100 Hidden Volcanoes

As ice recedes, hidden volcanoes under Antarctica awaken, reshaping predictions for climate change.

This Hornet Can Drink 80% Alcohol Without Ever Getting Drunk and Scientists Finally Know Why

Oriental hornets never get intoxicated with alcohol no matter how strong the alcohol or how long they drink.

200 Jurassic-era dinosaur footprints unearthed on UK’s largest dinosaur highway

Thanks to a storm, these dinosaur footprints managed to remain preserved for 166 million years.

The Soviets sent most of its intellectuals to remote gulags. Decades later, those areas became more prosperous

A new study reveals that regions near Soviet GULAG camps are more prosperous today, thanks to the unintended legacy of intellectual capital of educated prisoners

Strange Painted Penis Bone Found in England Reveals Rituals From Roman Britain

An enigmatic artifact suggests ancient rituals tied to fertility and agricultural cycles.