This parasitic 'blob' is the only known animal that doesn't breathe

Jan 3, 2020
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A genomic analysis of the creepy parasite H. salminicola reveals that the creature has no mitochondrial DNA and no way to breathe — two animal firsts.

This parasitic 'blob' is the only known animal that doesn't breathe : Read more
The paper is paywalled, but it seems myxozoan life cycles go through sexual actinospore stages and vegetative stages [ http://folia.paru.cas.cz/artkey/fol-200601-0001_myxozoan_genera_definition_and_notes_on_taxonomy_life-cycle_terminology_and_pathogenic_species.php ] and that we are looking at the latter being ~ 10 um [ https://fishpathogens.net/pathogen/henneguya-salminicola ].

As a comparison human skin cells average ~ 30 um, so these "suckers" ["stingers"?] should have minimized the genome size that in turn typically decide cell size.
 
Feb 25, 2020
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Somewhat puzzling. What about anaerobic bacteria? Is the author of this article presuming that they are really aerobic, or that they aren't animals? They are certainly lifeforms and they contain no chlorophyll so they aren't plants. Seems like some effort is being made to make H. Salminicola look a lot uniquer than it actually is.
 
Feb 19, 2020
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A genomic analysis of the creepy parasite H. salminicola reveals that the creature has no mitochondrial DNA and no way to breathe — two animal firsts.

This parasitic 'blob' is the only known animal that doesn't breathe : Read more
OK Where are these parasites mainly found (bodies of water) and how do they affect the fish to where we can identify them, and how do they affect the human when eating fish with this parasite? Can humans get infected by this parasite?
I have trouble comprehending all this above my intelligence, so please make it simple for me to comrhend
 
Feb 25, 2020
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Somewhat puzzling. What about anaerobic bacteria? Is the author of this article presuming that they are really aerobic, or that they aren't animals? They are certainly lifeforms and they contain no chlorophyll so they aren't plants. Seems like some effort is being made to make H. Salminicola look a lot uniquer than it actually is.
By "animals" they are referring the eukaryotes, which contain organelles like nuclei and mitochondria. Bacteria are prokaryotes. You are correct that bacteria do not contain mitochondria - an interesting evolutionary story unto itself. Google "mitochondria and bacteria ".
 
Feb 25, 2020
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Somewhat puzzling. What about anaerobic bacteria? Is the author of this article presuming that they are really aerobic, or that they aren't animals? They are certainly lifeforms and they contain no chlorophyll so they aren't plants. Seems like some effort is being made to make H. Salminicola look a lot uniquer than it actually is.
Bacteria are not animals - they're unicellular prokaryotes. This is a big exception to an otherwise universal rule. Pretty incredible, actually.
 
Jan 3, 2020
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Bacteria are not animals - they're unicellular prokaryotes. This is a big exception to an otherwise universal rule. Pretty incredible, actually.
Yes, especially incredible considering the relatively recent false alarm of (10 times as large) Loriciferans from anoxic mud - who turned out to be dead specimens.

There is no rule in biology without exceptions, including this one. (So there are some population genetics laws for equilibrium conditions, but outside of equilibrium ... well, the analogous conditions work as laws in thermodynamics so YMMV.)
 
Feb 25, 2020
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A genomic analysis of the creepy parasite H. salminicola reveals that the creature has no mitochondrial DNA and no way to breathe — two animal firsts.

This parasitic 'blob' is the only known animal that doesn't breathe : Read more
1) Myxozoans have been known for quite some time (the taxonomic Class was erected in the 1970s), and it has been known since they were first discovered that they have no mitochondria. Therefore, it has been known since soon after they were first discovered that they are obligate anaerobes.

This would make them unique among Metazoans (i.e., animals). However, Myxozoans are rather odd Metazoans in the first place (in fact, for a long time they were considered protozoans). This is probably due to the the fact that they are obligate parasites (parasites are often very highly derived, and sometimes almost unrecognizable as members of their higher taxonomic groups). For instance, Myxozoans, although Cnidarians, were not recognized as such until about two decades ago.

2) Cellular respiration and "breathing" are two different things. Cellular respiration is when glucose is metabolized. If that metabolization involves oxygen, it is considered aerobic respiration; if it doesn't utilize oxygen, it is considered anaerobic respiration. "Breathing" is the mechanical movement of air in and out of the body. The term can also be used to refer to the movement of oxygenated water over specialized gills. While both cellular respiration and "breathing" are called "respiration" they are NOT the same thing. There are many metazoans that do not breathe (or even have specialized gills). These organisms get their oxygen via simple diffusion over the body wall. In fact, this is true for most (all?) Cnidarians -- the Phylum to which Myxozoans belong. However, ALL living organisms have some sort of cellular respiration; in the case of Myxozoans that respiration is anaerobic.

3) The cool finding here is that there are no remnants of mitochondrial genes in the Myxozoan genome. Since the phylogenetic of the Myxozoa indicates that they are derived from Cnidarians, and all other Cnidarians are aerobic, this is a bit puzzling. Normally one would expect there to be some remnants of disused genes, even if their initial deactivation was in the distant past.
 
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Dec 8, 2019
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I never realized the diversity of the definition for an animal. It appears that any organism that is not classified as Plants, Fungi, Protista, Bacteria, or Archaea is an animal.
 
Jan 21, 2020
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1) Myxozoans have been known for quite some time (the taxonomic Class was erected in the 1970s), and it has been known since they were first discovered that they have no mitochondria. Therefore, it has been known since soon after they were first discovered that they are obligate anaerobes.

This would make them unique among metazoans (i.e., animals). However, Myxozoans are rather odd metazoans in the first place (in fact, for a long time they were considered protozoans). This is probably due to the the fact that they are obligate parasites (parasites are often very highly derived, and sometimes almost unrecognizable as members of their higher taxonomic groups). For instance, Myxozoans, although Cnidarians, were note recognized as such until about two decades ago.

2) Cellular respiration and "breathing" are two different things. Cellular respiration is when glucose is metabolized via oxidative reactions. "Breathing" is the mechanical movement of air in and out of the body. The term can also be used to refer to the movement of oxygenated water over specialized gills. While both are called "respiration" they are NOT the same thing. There are many metazoans that do not breath (or even have specialized gills), and get their oxygen via simple diffusion over the body wall. In fact, this is true for most Cnidarians -- the Phylum to which Myxozoans belong.

3) The cool finding here is that there are no remnants of mitochondrial genes in the Myxozoan genome. Since the phylogenetic of the Myxozoa indicates that they are derived from Cnidarians, and all other Cnidarians are aerobic, this is a bit puzzling -- normally one would expect there to be some remnants to disused genes, even if their initial deactivation was in the distant past.
I enjoyed your informative answers, I learned a lot! You are one smart raccoon 🦝!
 
Feb 25, 2020
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I never realized the diversity of the definition for an animal. It appears that any organism that is not classified as Plants, Fungi, Protista, Bacteria, or Archaea is an animal.
No. Biologists define Metazoans (animals) as members of a clade of multicellular heterotrophs. From a strictly evolutionary (or phylogenetic) perspective, Metazoans are all the organisms whose most recent common ancestor is at the base (or origin) of the Metazoan clade. This excludes Fungi, who are also multicellular heterotrophs; but have a different common ancestor. Myxozoans are barely multicellular, and were for some time considered to be colonial Protozoans. However, phylogenetic analyses indicate that their origin is well within the Cnidaria (jellyfish, anemones, et cetera), making them Cnidarians by definition (and thus Metazoans), regardless of whether they are multicellular or not.
 
Feb 26, 2020
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Somewhat puzzling. What about anaerobic bacteria? Is the author of this article presuming that they are really aerobic, or that they aren't animals? They are certainly lifeforms and they contain no chlorophyll so they aren't plants. Seems like some effort is being made to make H. Salminicola look a lot uniquer than it actually is.
SpinResistant, of course, there are other life forms that do not require oxygen but this is the first ANIMAL, an animal is a lifeform within the kingdom Animalia, as of now, this species is the only organism within Animalia (aka an animal) that does not require oxygen to survive. So it is actually unimaginably unique.
 
Feb 26, 2020
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I never realized the diversity of the definition for an animal. It appears that any organism that is not classified as Plants, Fungi, Protista, Bacteria, or Archaea is an animal.
Yes but, there's a classification for an animal, it is an organism within the kingdom of Animalia. it is not a very diverse definition, look more into Protists, that is a kingdom with by far the most organisms that are diverse, the vast majority are not even somewhat related.
 
Feb 19, 2020
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There is a big difference between surviving without oxygen and requiring it to exist. All Metazoans need free oxygen to hydroxylate proline and lysine to synthesize the structural proteins... collagens. This parasite is no different. It has 'polar capsule' nematocysts that have 'minicollagen'. That means it needs free oxygen. at some point. The fact that it lost? an ability to "breath" is what seems to be the "big deal".
 
Feb 28, 2020
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I never realized the diversity of the definition for an animal. It appears that any organism that is not classified as Plants, Fungi, Protista, Bacteria, or Archaea is an animal.
Myxozoa are bona fide animals in the strict phylogenetic sense - they are very very unusual animals in terms of organismal organisation, but they are descended from large multicellular things that you would recognise as animals without a second thought.
 
Feb 28, 2020
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By "animals" they are referring the eukaryotes, which contain organelles like nuclei and mitochondria. Bacteria are prokaryotes. You are correct that bacteria do not contain mitochondria - an interesting evolutionary story unto itself. Google "mitochondria and bacteria ".
Further, they are referring to animals in the strict sense. There are already a LOT of non-animal unicellular eukaryotes ("protists") known that have no mitochondrial DNA, and in at least one case, seem to have no mitochondrion at all [https://www.ncbi.nlm.nih.gov/pubmed/27185558]. So this is an exciting and important first discovery for the 'animal clade', but is not a new finding for eukaryotes at large.
 
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Feb 28, 2020
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Somewhat puzzling. What about anaerobic bacteria? Is the author of this article presuming that they are really aerobic, or that they aren't animals? They are certainly lifeforms and they contain no chlorophyll so they aren't plants. Seems like some effort is being made to make H. Salminicola look a lot uniquer than it actually is.
Anaerobic bacteria are unicellular whereas "animals" are typically thought of as multicellular. In the multicellular world, the lack of mitochondrial oxidative pathway is unusual.
 
Feb 19, 2020
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Why this is exciting and important is a puzzle. A tiny parasite that has lost the ability to need free oxygen to survive but requires it to exist?
 
Feb 25, 2020
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There is a big difference between surviving without oxygen and requiring it to exist. All Metazoans need free oxygen to hydroxylate proline and lysine to synthesize the structural proteins... collagens. This parasite is no different. It has 'polar capsule' nematocysts that have 'minicollagen'. That means it needs free oxygen. at some point. The fact that it lost? an ability to "breath" is what seems to be the "big deal".
Not quite. From the abstract of the PNAS article:

"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."

So, for this particular species and perhaps for myxozoans in general, the ability of metabolize via aerobic respiration has been completely lost. Again, cellular respiration is NOT the same as "breathing".

As for the synthesis of collagen, it is true that free O2 is necessary for collagen synthesis in KNOWN anabolic pathways. However, it is possible that myxozoans may have some novel pathway that gets around this constraint. In any case, that myxozoans have completely lost their mitochondrial genome is a very cool finding.
 
Feb 25, 2020
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Yes but, there's a classification for an animal, it is an organism within the kingdom of Animalia. it is not a very diverse definition, look more into Protists, that is a kingdom with by far the most organisms that are diverse, the vast majority are not even somewhat related.
"Protista" and "Protoctista" are no longer considered to be valid taxa for just this reason.
 
Feb 25, 2020
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Why this is exciting and important is a puzzle. A tiny parasite that has lost the ability to need free oxygen to survive but requires it to exist?
Because myxozoans appear to be the ONLY metazoans to have completely lost their mitochondria, and to have completely lost the genes involved in the synthesis of mitochondria. Therefore they are the ONLY metazoans to have completely lost their ability to aerobically respire.
 
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Feb 19, 2020
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Yes, NgNg, it is always possible that this little parasite got around the need for free oxygen in all known pathways, but also to synthesize two amino acids not in the genetic code that make collagens possible. That is unique, not only to Metazoa but also to Metaphyta where the exact same enzyme cofactors are used. to make higher plant structural proteins. But, it took a very long time, (geologically speaking) for any organism to evolve that process. There is no structural protein substitute. Yes, It is a "cool finding" but phylogenetically puzzling. Why would some tiny parasitic organism that needs free oxygen at some point to even exist want to lose the aerobic pathway that is so useful in a world now filled with free oxygen?

"As for the synthesis of collagen, it is true that free O2 is necessary for collagen synthesis in KNOWN anabolic pathways. However, it is possible that myxozoans may have some novel pathway that gets around this constraint. In any case, that myxozoans have completely lost their mitochondrial genome is a very cool finding."
 

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