Scientists discover first oxygen-free parasite living inside Salmon

H. salminicola, a parasite live without oxygen inside salmon. (Image: Stephen Douglas Atkinson)

Researchers have discovered a parasite, Henneguya salminicola, living without oxygen inside salmon muscles. This finding upends biology’s belief that all animals need oxygen to survive. H. salminicola lacks a mitochondrial genome and uses anaerobic energy production instead.

A Strange Life Hidden in Salmon Flesh

H. salminicola belongs to jellyfish- and coral-related lineages. Yet this parasite lost typical animal respiration during evolution. Scientists found no mitochondrial DNA inside its cells. Instead, it relies on a completely different, unknown energy mechanism.

How It Survives With No Oxygen?

Living inside salmon muscles offers a low-oxygen, nutrient-rich environment. The parasite likely absorbs energy directly from its host’s cells. Its simplified body reduces energy demands drastically compared to normal animals.

Why This Discovery Matters? 

This overturns the long-held idea that oxygen is essential for animal life. It shows complex multicellular life can adapt to oxygen-free conditions. Biologists must rethink definitions of life and survival on Earth.

Life Redefined For Other Worlds

If animals can survive without oxygen on Earth, aliens might too. Searches for extraterrestrial life may expand to oxygen-free planets or moons. This broadens criteria for habitable worlds and astrobiology studies.

What Scientists Want to Learn Next? 

Research now aims to decode the parasite’s anaerobic metabolism. Understanding its biochemistry could unlock new insights into life’s flexibility. The study may influence future biology research and astrobiology exploration.