Scientists Discover First-Ever Animal On Earth That Doesn't Breathe

Most multicellular organisms on earth whose DNA has been sequenced possess respiratory genes. But those organisms like this newly-discovered which lives its life infecting the dense muscle tissues of fish and underwater worms wouldn’t have much opportunity to perform aerobic respiration.

Scientists at Tel Aviv University in Israel have discovered that aerobic respiration – which is one of the predominant metabolic pathways isn’t ubiquitous among animals anymore. Via deep sequencing approaches, they have discovered a member of the Cnidaria, the myxozoan named Henneguya salminicola which lacks a mitochondrial genome and the ability to perform aerobic cellular respiration. In simple terms, this organism doesn’t breathe.

According to the research team who discovered it, the organism provides an opportunity for understanding the evolutionary transition from aerobic to an exclusive anaerobic metabolism.

Similar to several parasites from the myxozoa class which includes simple microscopic swimmers distantly associated with jellyfish, the H. salminicola might have resembled its jelly ancestors and gradually evolved to have just none of its multicellular traits. Fish infected with this organism are said to have ‘tapioca disease.’

“They have lost their tissue, their nerve cells, their muscles, everything. And now we find they have lost their ability to breathe,” Live Science quoted the study co-author Dorothée Huchon, an evolutionary biologist at Tel Aviv University in Israel. “Animals are always thought to be multicellular organisms with lots of genes that evolve to be more and more complex. Here, we see an organism that goes completely the opposite way. They have evolved to be almost unicellular," he added.

The authors highlighted the fact that H.salminicola not only lost its mitochondrial genome but also all of its nuclear genes pertaining to transcription and replication of the mitochondrial genome. They happened to identify several genes encoding for proteins pertaining to other mitochondrial pathways.

So, how does H.salminicola acquire energy without breathing?

Although the researchers aren’t really sure about it, they opine that other similar parasites possess proteins that have the capability of importing ATP or molecular energy directly from their infected hosts. This animal could be doing something similar. However, further studies are required to completely understand its mechanism.