Meet Henneguya Salminicola: The Only Known Multicellular Organism That Can Live Without Oxygen


H. salminicola is the only known multicellular organism to be able to survive without oxygen (Credit: Stephen Douglas Atkinson)

Though many single-celled lifeforms have evolved to survive without oxygen, multicellular organisms have always been believed to need it to live. Now, scientists in Tel Aviv, Israel, have found that Henneguya salminicola, a parasite, which spends its life attached to the muscle tissue of fish, has adapted to living without oxygen.

Dorothee Huchon, a molecular geneticist at Tel Aviv University, and her colleagues stumbled upon the discovery accidentally while investigating the mitochondrial genes of the tiny H. salminicola, which comprises fewer than ten cells. Commonly dubbed "the powerhouse of the cell," mitochondrion help break down the oxygen we breathe in to create adenosine triphosphate (ATP), a chemical that provides the energy needed for many of the fundamental processes of living cells, including muscle contraction.

However, when the researchers stained the H. salminicola cells with a blue fluorescent dye that binds to DNA, they found no DNA visible in cells outside the nucleus. In contrast, the same test on some closely-related parasites revealed tiny blue dots corresponding to mitochondrial genomes outside the nucleus. Though further investigation revealed structures resembling mitochondria in the H. salminicola, they were incapable of producing the enzymes needed for respiration.

"We don't know why H. salminicola has lost this ability while all of its immediate relatives that we have identified use oxygen. As these parasites move through their life cycle, they may also live inside a worm host where they would have to make do with virtually no oxygen, as well. The worm host of H. salminicola has never been identified, but it too may live in sediments with very low oxygen levels," says Prof. Huchon.

The blue fluorescent dye showed normal nuclear DNA (glowing blue circles) of the H. salminicola. However, there were no mitochondria present, which would be visible as many smaller blue dots near the larger circles (Credit: Stephen Douglas Atkinson)

The Tel Aviv scientists, who published their findings in the journal Proceedings of the National Academy of Sciences on February 10, 2020, are still unsure how H. salminicola generates energy. "It's not yet clear to us how the parasite generates energy," Prof. Huchon says. "It may be drawing it from the surrounding fish cells, or it may have a different type of respiration such as oxygen-free breathing, which typically characterizes anaerobic non-animal organisms."

Regardless of the mechanism used, the professor believes the discovery is extremely significant for evolutionary research. "It is generally thought that during evolution, organisms become more and more complex, and that simple single-celled or few-celled organisms are the ancestors of complex organisms," she says. "But here, right before us, is an animal whose evolutionary process is the opposite. Living in an oxygen-free environment, it has shed unnecessary genes responsible for aerobic respiration and become an even simpler organism."

Fluorescence micrograph of the H. salminicola spores. The fluorescent dye has penetrated the spore nuclei and membranes (Credit: Stephen Douglas Atkinson)

A distant cousin of the jellyfish, H. salminicola is a fairly common parasite that causes white cysts, or "tapioca disease," on the flesh of fish, such as the adult Chinook and the coho salmon. Though unsightly, the tiny bubbles, which ooze a creamy white liquid filled with many microscopic myxozoan spores when ruptured, are generally harmless to humans and the fish itself.


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  • 5000unicorns
    5000unicornsTuesday, July 21, 2020 at 4:32 pm
    • wolfieland
      wolfielandFriday, July 10, 2020 at 9:41 am
      so pretty
      • l78
        l78Tuesday, June 9, 2020 at 5:44 am
        Wow! Amazing!
        • coolvae
          coolvaeTuesday, July 21, 2020 at 12:18 pm
          wow! this animal can't breathe.
        • neverkid
          neverkidTuesday, June 9, 2020 at 2:25 am
          There's no oxygen in space space right? Maybe they could be related to organisms in space? Aliens, perhaps, evolved from these creatures!
          • leiker1414
            leiker1414Sunday, July 5, 2020 at 1:12 pm
            Nope but there is also no gravity. U should watch the movie the 100 it is my favorite movie.
            • leiker1414
              leiker1414Sunday, July 5, 2020 at 1:14 pm
              They are in space and on earth 🌎 it on Netflix. You might not be able to watch it but if u can i recommend it
          • citizenofheaven
            citizenofheavenWednesday, June 3, 2020 at 1:35 pm
            yay! go Israel!
            • i_like_fruit
              i_like_fruitFriday, May 29, 2020 at 6:43 am
              Wow! This is cool and neat. Like and follow if you agree.
              • prather1234ps
                prather1234psWednesday, May 27, 2020 at 9:18 am
                • l78
                  l78Thursday, May 21, 2020 at 2:43 pm
                  COO!!!!(AKA cool!!!)
                  • leiker1414
                    leiker1414Friday, July 3, 2020 at 5:12 pm
                    my brother always says that.
                  • effie302
                    effie302Friday, May 15, 2020 at 7:43 am
                    so...... fantastic
                    • lilabug
                      lilabugSunday, May 10, 2020 at 12:18 pm
                      Wow! So weird and cool at the same time!