Scientists discover first oxygen-free parasite living inside Salmon

A tiny salmon parasite has become the first animal proven to survive without oxygen, overturning long-held biology assumptions and reshaping how scientists define life.

December 01, 2025 / 17:47 IST
Story continues below Advertisement
H. salminicola, a parasite live without oxygen inside salmon. (Image: Stephen Douglas Atkinson)
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

Story continues below Advertisement

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?