Scientists find first Animal life that does not need Oxygen:

[beecee]

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Scientists Find The First-Ever Animal That Doesn't Need Oxygen to Survive

 

MICHELLE STARR

25 FEB 2020

Some truths about the Universe and our experience in it seem immutable. The sky is up. Gravity sucks. Nothing can travel faster than light. Multicellular life needs oxygen to live. Except we might need to rethink that last one.

 

Scientists have just discovered that a jellyfish-like parasite doesn't have a mitochondrial genome - the first multicellular organism known to have this absence. That means it doesn't breathe; in fact, it lives its life completely free of oxygen dependency.

more at link.....

 

https://www.pnas.org/content/early/2020/02/18/1909907117

the paper:

A cnidarian parasite of salmon (Myxozoa: Henneguya) lacks a mitochondrial genome:

 

Significance

Mitochondrial respiration is an ancient characteristic of eukaryotes. However, it was lost independently in multiple eukaryotic lineages as part of adaptations to an anaerobic lifestyle. We show that a similar adaptation occurred in a member of the Myxozoa, a large group of microscopic parasitic animals that are closely related to jellyfish and hydroids. Using deep sequencing approaches supported by microscopic observations, we present evidence that an animal has lost its mitochondrial genome. The myxozoan cells retain structures deemed mitochondrion-related organelles, but have lost genes related to aerobic respiration and mitochondrial genome replication. Our discovery shows that aerobic respiration, one of the most important metabolic pathways, is not ubiquitous among animals.

Abstract

Although aerobic respiration is a hallmark of eukaryotes, a few unicellular lineages, growing in hypoxic environments, have secondarily lost this ability. In the absence of oxygen, the mitochondria of these organisms have lost all or parts of their genomes and evolved into mitochondria-related organelles (MROs). There has been debate regarding the presence of MROs in animals. Using deep sequencing approaches, we discovered that a member of the Cnidaria, the myxozoan Henneguya salminicola, has no mitochondrial genome, and thus has lost the ability to perform aerobic cellular respiration. This indicates that these core eukaryotic features are not ubiquitous among animals. Our analyses suggest that H. salminicola lost not only its mitochondrial genome but also nearly all nuclear genes involved in transcription and replication of the mitochondrial genome. In contrast, we identified many genes that encode proteins involved in other mitochondrial pathways and determined that genes involved in aerobic respiration or mitochondrial DNA replication were either absent or present only as pseudogenes. As a control, we used the same sequencing and annotation methods to show that a closely related myxozoan, Myxobolus squamalis, has a mitochondrial genome. The molecular results are supported by fluorescence micrographs, which show the presence of mitochondrial DNA in M. squamalis, but not in H. salminicola. 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.

Edited February 26, 2020 by beecee

[CharonY]

I have read the PNAS paper which is interesting, but by golly,  I do dislike the blurbs some people come up with (and I was so sure that it would happen like this).

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Multicellular life needs oxygen to live. Except we might need to rethink that last one.

Anaerobic multicellular life forms have been described earlier.  As a matter of fact, about ten years ago, where it also went through the news and you can find frigging Wiki pages on them. The authors of the papers write:

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 Although it was reported that some loriciferans found in anoxic conditions possess hydrogenosomes (4, 5), genomic data are not yet available for these organisms, and alternative explanations have been proposed (3). 

How hard can it be to write a blurb after reading at least a few sentences of the intro to get the context right? I should also add that this is a bit of a pet peeve of mine and may not be considered as critical as others. Many students and even young scientists have the tendency to only dig up and cite recent papers and as a consequence kind of re-invent the wheel multiple times. This creates a kind of community-based amnesia that sometimes publishes rather well known phenomena as something surprising or new. While it is rarely happening in the leading journals in the respective fields, I (subjectively) seem to find an increasing number of them in more multi-disciplinary areas, which I kind eminently disappointing.... (OK end of rant, I promise).  

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That means it doesn't breathe; in fact, it lives its life completely free of oxygen dependency.

This part is a bit trickier as laypersons often conflate, aerobic respiration, anaerobic respiration, breathing and similar terms. Part of it is because sometimes scientists like to use simple terms to make things more easy to understand and it is understandable that most folks probably do not learn much about anaerobic respiration (i.e. the use of electron donors other than oxygen). However, considering that the authors specifically mentioned aerobic respiration and made few assumption regarding how the organism obtains energy I would have welcomed it if the author of the blurb would have either stuck to the fact that without functional mitchondria (actually they specifically lack mitochondrial DNA; membrane structure remnants were still observed) they are unable to use oxygen and left the breathing part out, or used the space to explain the context in another one or two sentences or so. But I acknowledge that this is a minor issue.