Related: What's the biggest obligate anaerobic organism discovered till now?

I had always assumed that the Riftia tube worms were obligately anaerobic since they lived next to anoxic volcanic vents, but a quick literature search showed it to be a facultative anaerobe, being able to survive at least 60 hours without oxygen.

If "facultative anaerobe" is defined as being able to survive at least 24 hours in the absence of molecular oxygen in an otherwise normal environment, are there any metazoal organisms larger than Riftia (which are up to 1.5m long)?

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    $\begingroup$ The answer to your question is going to be some plant or fungus. You might want to stick the word "metazoan" somewhere in your question. $\endgroup$
    – tel
    Dec 17, 2014 at 22:52
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    $\begingroup$ Tapeworms? They can grow much longer. Are you specifically interested in free living metazoans? $\endgroup$
    Dec 18, 2014 at 4:19
  • $\begingroup$ I didn't specifically ask for free-living metazoans, so tapeworms would be a good answer. $\endgroup$
    – March Ho
    Dec 18, 2014 at 7:06
  • $\begingroup$ @MarchHo am not able to find a reliable evidence for the anaerobic metabolism in large cestodes. $\endgroup$
    Dec 18, 2014 at 11:05

1 Answer 1


I think a tapeworm is your best bet. For tapeworms specifically, I found this textbook, Animal Physiology: From Genes to Organisms, which claims:

Active facultative anaerobes include some parasitic worms such as tapeworms that can survive without oxygen indefinitely...

I was not able to find any primary research on the subject either @WYSIWYG (other than a paper from 1951 that doesn't seem to be available anywhere), but if the textbook's claim holds, I can't think of anything larger than a tapeworm.


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