Researchers have uncovered a multicellular eukaryote that lacks mitochondria, Ars Technica reports.
In their Proceedings of the National Academy of Sciences paper, a team led by Tel Aviv University's Dorothée Huchon note that though aerobic respiration is "a hallmark of eukaryotes," some unicellular lineages living in low-oxygen environments have lost this ability, replacing it with anaerobic metabolic processes.
By sequencing two related freshwater species — the Henneguya salminicola and Myxobolus squamalis, which are Myxozoans and parasites of salmonid fish — the researchers found that H. salminicola has lost its mitochondrial genome. They note, though, it has retained a mitochondrion-like organelle, but lacks the genes needed for aerobic respiration and the nuclear genes needed for mitochondrial genome replication. M. squamalis, meanwhile, has a mitochondrial genome.
This finding, the researchers write, indicates that "adaptation to an anaerobic environment is not unique to single-celled eukaryotes, but has also evolved in a multicellular, parasitic animal" and that H. salminicola "provides an opportunity for understanding the evolutionary transition from an aerobic to an exclusive anaerobic metabolism."