Countless strange, and often alien-like, animals have been discovered across the world, but all of them have had a few, core physiological characteristics in common. One of those characteristics is the need for oxygen, in order to carry out cellular respiration, or the chemical processes that convert energy stored in nutrients into a usable form. But now, researchers from the U.S. and Israel have announced they’ve discovered an animal—more specifically, a parasite—that doesn’t require oxygen to survive.
Metro picked up on word of the sans-oxygen animal, which was announced in a paper recently published in the journal, Proceedings of the National Academy of Sciences of the United States of America. In the paper, the authors, including Dayana Yahalomi of Tel Aviv University, Stephen D. Atkinson of Oregon State University, Corvallis, et al., focus on Henneguya salminicola, a putrid-looking species of parasite that shows up in certain species of salmon. And also, somehow, manages to do what no other known animal (which is defined as a multicellular eukaryotic organism) can.
H. salminicola / Stephen Douglas Atkinson
In the abstract for the paper, the authors note that they used “deep sequencing approaches” to confirm that H. salminicola doesn’t have any mitochondrial DNA, and, as a consequence, has “lost the ability to perform aerobic cellular respiration.” Which not only means that H. salminicola doesn’t need oxygen to live, but also “indicates that [some] core eukaryotic features are not ubiquitous among animals.”
For those who think they’ve seen news of completely anaerobic animals before, that’s probably because of a 2010 study, in which Italian and Danish researchers described three new marine species belonging to the phylum, Loricifera, which is made up of microscopic or nearly microscopic sediment-dwelling animals. But while that study concluded that the newly discovered species of Loricifera were completely without mitochondria, those researchers did not actually sequence the tiny creatures’ mitochondrial DNA to confirm that fact. And that’s where that study and this one differ.
Dorothée Huchon, the professor from Tel Aviv University who first discovered the fact that H. salminicola lacks mitochondrial DNA, said in an interview (above), that all of her and her co-authors’ findings are confirmed by genomic results, while the results of others who’ve claimed to have found completely anaerobic animals are not. Incidentally, she also mentions in the interview that she made the discovery inadvertently. She wasn’t necessarily looking for an animal fully lacking mitochondrial DNA.
Huchon also points out in the interview that H. salminicola is an example of a species that evolved to become less complex over time rather than more complex, in order to survive in its environment inside of fish muscles. This transition, whereby H. salminicola evolved from an animal type that did require oxygen to survive, is still mysterious. Hopefully it will become clearer now thanks to this discovery.
Fluorescence micrographs of H. salminicola. Stephen D. Atkinson
As for what Huchon is up to now, she says that she and her colleagues will continue to study H. salminicola and other parasites like it, as they can cause significant damage to aquaculture, especially in the Mediterranean Sea.
What do you think about these newly discovered fully anaerobic animals? Do they give you more hope for finding life on alien worlds? Or maybe even make you question the way we classify animals? Let us know your thoughts in the comments!
Images: Stephen D. Atkinson via i24NEWS English