A new branch of animal life is discovered
April 8, 2010 2:31 PM   Subscribe

Meet three new species of Loricifera, the first multicellular forms of life found that can live entirely without oxygen (figures and full article, PDF).

Why is this major? This is the first multicellular organism discovered without mitochondria, cellular organelles which facilitate aerobic respiration, i.e. allow life to burn food with the help of oxygen.

There are many forms of bacteria (prokaryotes) that can do anaerobic respiration, as well as a few single-celled anaerobic eukaryotes like Giardia and Trichomonas vaginalis, but no multicellular organisms — until now.

It is widely believed that the ancestor of all eukaryotes (cells with nuclei) engulfed and retained an Alphaproteobacteria and that the descendants of that engulfed bacteria became mitochondria — and the descendants of that host became the group we now call eukaryotes.

Single-celled eukaryotes that live in low- or no-oxygen environments often lack mitochondria but possess a "hydrogenosome", an organelle that resembles mitochondria and functions like its anaerobic equivalent, helping to turn food into energy (but without the help of oxygen).

There is debate about the evolution of these hydrogenosomes, though it is mostly thought that mitochondria in an anaerobic eukaryote lost the enzymes necessary for aerobic respiration, retaining those needed for anaerobic respiration (such as pyruvate-ferrodoxin oxidoreductase, used for reducing pyruvate which is thought to have been in ample supply in a prebiotic Earth). Alternatively, hydrogenosome-containing eukaryotes may represent a completely distinct lineage of eukaryotes from the mitochondrial lineage.

One hypothesis is that these organisms share a common ancestor with jellyfish or some other common multicellular eukaryote. These organisms must then have either undergone endosymbiosis with a single-celled anaerobe (much like what is hypothesized to have happened with mitochondria) or undergone convergent evolution to develop robust hydrogenosome-like functionality.

Another hypothesis, (which, while much less likely, would be by far the most groundbreaking result, if true) is if these organisms represent a completely new multicellular animal that evolved more directly from an anaerobic ancestor with a hydrogenosome.

No matter which evolutionary path these organisms took to get where they are today, studies of loriciferans are likely to alter our understanding of the diversity of life in fundamental ways.
posted by Blazecock Pileon (29 comments total) 44 users marked this as a favorite
Awesome post, Blazecock Pileon. I would rate this discovery as even more significant than that of an exoplanet of earthlike size and orbit (which hasn't happened yet but will receive far more ballyhoo than this when it does). Like the discovery of the seafloor "smoker" ecologies before it, this just blows away our prior ideas about what's required for life and what kinds of environments are actually habitable. More things than are dreamt of in [our] philosophy...
posted by dust of the stars at 2:38 PM on April 8, 2010 [2 favorites]

I forgot to add this Nature news clip, which adds a little bit more information.
posted by Blazecock Pileon at 2:41 PM on April 8, 2010

Sure, if you call that living.
posted by notmydesk at 2:45 PM on April 8, 2010 [8 favorites]


/Mr. Spock
posted by Splunge at 2:48 PM on April 8, 2010

I, for one, welcome our new anaerobic overlords.
posted by wcfields at 2:53 PM on April 8, 2010

I would wonder if they are derived from mitochondria-bearing ancestors and the lack of mitochondria in the anaerobes is a derived form. Use it or lose it, and all that. That would probably mean that there would be fossil evidence of some precursor in some dusty museum draw. That would be another interesting find.
posted by kuujjuarapik at 2:58 PM on April 8, 2010

They're very small. Can they be underlords?
posted by fantabulous timewaster at 3:00 PM on April 8, 2010

Wow. I love that most of the paper consists of them testing whether or not the specimens were alive.

I am not a taxonometerist, but can someone explain why something showing this novel a phenomenon doesn't rate a new genus?
posted by PMdixon at 3:00 PM on April 8, 2010

PMdixon, the 'nov. sp.' after their names means that these are proposed names. They are probably going to get new official Genus and species names, but as I recall there are some peer review conventions for naming that take some time.
posted by kuujjuarapik at 3:14 PM on April 8, 2010 [1 favorite]

I fucking love this post. Extremophile retention of a metabolic pattern that predates atmospheric oxygen! Wierd non-mitochondrial symbiotes! Cool.

I would have liked to have seen some more molecular-level details about the loriciferians' redox metabolism than were provided by the paper, but I'm sure that'll be forthcoming.
posted by killdevil at 3:15 PM on April 8, 2010

What do they taste like?
posted by infinitywaltz at 3:16 PM on April 8, 2010 [2 favorites]

So are these the guys that will lead the counter-revolution when the mitochondria achieve consciousness and consume the world? /semi-obscure game references
posted by Caduceus at 3:29 PM on April 8, 2010

What do they taste like?

They taste YOU! Therefore, you taste yourself. Infinite loop. Human sacrifice, dogs and cats living together... mass hysteria!
posted by Splunge at 4:04 PM on April 8, 2010

What do they taste like?

posted by killdevil at 4:05 PM on April 8, 2010

Oh, and also? Acid for blood.
posted by It's Raining Florence Henderson at 4:22 PM on April 8, 2010

I bet they taste like a mixture of mud and hagfish poop.
posted by kuujjuarapik at 4:53 PM on April 8, 2010 [1 favorite]

Life will find a way, a horrible, horrible way.
posted by The Whelk at 5:45 PM on April 8, 2010 [2 favorites]

Thank you for the post. This is tres cool.
posted by ltracey at 7:00 PM on April 8, 2010

18 comments so far, and not a single Republican joke.
posted by ZenMasterThis at 7:11 PM on April 8, 2010

We don't wanna insult this newly found life-form with the comparison.
posted by The Whelk at 8:27 PM on April 8, 2010

Along Republican lines, life can irrevocably alter Earth's environment to the point where it wipes out damn near everything that came before... the Great Oxygenation Event, or as it's sometimes known, the Siderian Oxygen Catastrophe.

What would be really freaky is they were living fossils from before the Oxygen Catastrophe... creatures with a lineage two and a half BILLION years old, the last survivors of an ancient pre-cambrian period, that predates our pre-cambrian period by 1.8 billion years, that was abruptly ended when life turned its environment irreversibly toxic to itself. A divergently evolved multicellular organism would be too cool for school.
posted by Slap*Happy at 9:15 PM on April 8, 2010

Neat post, BP. I also hope these little guys are the last survivors of life before Earth got poisoned with oxygen (nasty reactive stuff, oxygen...) That would be even cooler than the coelecanth.

But it seems that these critters appeared after Earth went aerobic, since the hydrogenosome is thought to have evolved from the mitochondrion by ditching the machinery for aerobic metabolism (along with its DNA - oops! talk about co-dependent!) That's a hard way to earn a living, adapting to cold dark salty water with no oxygen. At least black smokers provide ample heat to drive chemosynthesis and even a tiny bit of light for photosynthesis. These little guys got a bum deal.
posted by Quietgal at 9:55 PM on April 8, 2010

When I was in 8th grade (circa 1991), I had to memorize both the periodic table of elements and most of the tree of life. Since then, there have been at least 10 new elements (including one last year) and this whole new domain of the tree of life, Archea, and extensive re-arranging within the branches.
Depending on whether these Loricfera are are derived from Eukaryotes or not, there may be another domain added on to that pendulous tree.
The Linnean minded 12 year old in me is pissed at all this new stuff that wasn't pounded into my head 20 years ago and wanting to ignore it, but the scientist is deeply deeply excited.

The scientist however has a few quibbles. There isn't any evidence that the Loricferens lack mitochondria... the only figures they show are scanning EMs of hydrogenosome-like objects. A few negative degenerate PCRs of mtDNA starting from a likely ciliate or nematoda would be helpful. (a negative degenerate PCR is a very easy thing to get) Given their living conditions, they would likely have lost them. For phylogenetic reasons alone, this could be a compelling data point. Further, sequencing a genome is almost trivial today, so why haven't they made any sequence comparisons to Nyctotherus ovalis, for analogy, if not exclusion?
Additionally, as the authors are calling them nemotodes etc, it seems that they've already deemed that they are a derived eukaryote and are not trying to bud off a more basal branch on the tree of life.
posted by Cold Lurkey at 10:16 PM on April 8, 2010 [1 favorite]

I have got awesome anaerobic fitness.
posted by uncanny hengeman at 10:42 PM on April 8, 2010

Sorry, what I meant to say was:

"You tell everybody. Listen to me, Blazecock Pileon. You've gotta tell them!

Loricifera is people!

We've gotta stop them somehow!"

posted by uncanny hengeman at 10:49 PM on April 8, 2010

Gizmodo's headline, IIRC, was something like "life on other planets now basically for sure". It certainly demolishes the (to my mind always shaky) assumption that (multicellular) life implies oxygen (either for input or output).
posted by DU at 4:54 AM on April 9, 2010 [1 favorite]

What would be really freaky is they were living fossils from before the Oxygen Catastrophe... creatures with a lineage two and a half BILLION years old, the last survivors of an ancient pre-cambrian period, that predates our pre-cambrian period by 1.8 billion years

Yeah, that'd make it sound like the plot for Dan Brown's new novel.

Actually, it's amazing seeing discoveries, the repercussions of which will be fully understood after a long, long time.
posted by ersatz at 5:33 AM on April 9, 2010

Cold Lurkey, good point about not really proving the absence of mitochondria. My impression, though, is that the main point of this paper was to prove that these loricifera were actually alive, not just dead husks that drifted down from upper waters. Gotta establish the basics, especially when making such a startling claim. (Anaerobic metazoans? Paging H. P. Lovecraft!)

Also, references to nematodes were to, well, nematodes, which were used as control aerobic organisms from nearby oxygenated sediments since there weren't any loriciferans in those samples. Not related, just neighbors.

A deeply irresponsible part of me wants to load a rocket with these loriciferans and slam it into Europa, then check back in a hundred years or so. I demand life on other planets and I'm willing to cheat to get it. and I'll settle for a moon, too
posted by Quietgal at 6:22 AM on April 9, 2010 [1 favorite]

So this paper showed up on Faculty of 1000 yesterday (paywalled so no link) and the first reviewer said something that made me chuckle:
The Loricifera are one of the most recently discovered phyla, and their diversity is still barely known. They live in the interstices of soft bottoms...

In his defense, he doesn't seem to be a native english speaker, but I was laughing hard enough that I then had to explain the whole paper to my labmates. And then I got to use the phrase anoxic bottoms.

Good eye Blazecock.
posted by Cold Lurkey at 8:55 PM on April 15, 2010 [1 favorite]

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