US, WASHINGTON (ORDO NEWS) — Scientists have not yet figured out how this creature receives energy.
Scientists from Tel Aviv University have discovered an animal that does not need oxygen to breathe. A recently discovered species is the parasite Henneguya salminicola . It lives in the muscle tissue of salmon and consists of less than ten cells. This species has a common ancestor with jellyfish and, therefore, belongs to the creeping, but over millions of years of evolution it has become a much simpler creature that we see today.
Henneguya salminicola lost most of the original jellyfish genome, but, oddly enough, retained complex elements that resemble streak cells. However, the parasite uses them not to sting, but to cling to its owners. Although the cysts that form as a result of an animal’s activity in the salmon muscles are unsightly, the parasite is harmless and remains inside the fish throughout its entire life cycle.
Studying the animal, scientists found that Henneguya salminicola does not have a mitochondrial genome. This means that the parasite does not breathe in the known sense of the word and is completely free from oxygen dependence.
“Aerobic respiration was considered mandatory in animals, but now we have confirmed that this is not so. Our discovery shows that evolution can go in strange directions. Aerobic respiration is the main source of energy, and yet we found an animal that deviated from this path , ”says Dorothy Hutchon, co-author of the study.
Each cell in our body contains many mitochondria, which are necessary for breathing. They break down oxygen and use its energy to synthesize adenosine triphosphate, without which multicellular organisms cannot exist.
We know that there are devices that allow some organisms to thrive in conditions of low oxygen content, or hypoxia. Some unicellular mitochondria have turned into simplified organelles for anaerobic metabolism; but the possibility of the existence of anaerobic multicellular organisms has been the subject of scientific debate.
“It is not yet clear to us how the parasite generates energy. It can be taken from the surrounding fish cells, or Henneguya salminicola can have a different type of respiration, such as oxygen-free breathing, which is characteristic of unicellular anaerobes,” Dorothy Hutchon.
To study Henneguya salminicola, researchers used genome sequencing and fluorescence microscopy. In addition to the fact that the parasite lacked a mitochondrial genome, it turned out that, like unicellular organisms, it developed other organelles based on mitochondria.
The same sequencing and microscopy methods for the closely related parasite Myxobolus squamalis were used as a control and clearly showed the presence of the mitochondrial genome.
“Our discovery confirms that adaptation to the anaerobic environment is not unique to unicellular eukaryotes, but also develops in multicellular parasitic animals,” the researchers note.
“It is generally believed that during evolution, organisms become more and more complex, and that simple unicellular or“ small-cell ”organisms are the ancestors of complex organisms. But here, right in front of us, is an animal whose evolution has gone in the opposite direction. Living in an oxygen-free environment, he got rid of the unnecessary genes necessary for aerobic respiration, and became very simple, ” concludes Huchon.
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