Inhalation of oxygen is a fundamental characteristic of multicellular organisms. But there is at least one animal that does not have this ability and does without oxygen.
This amazing discovery is reported by an international team of biologists and geneticists in an article published in PNAS.
The organism in question is called Henneguya salminicola. This is a distant relative of jellyfish, a representative of the class Myxozoa – parasitic invertebrates belonging to the striking. The hosts of H. salminicola can be fish or worms that live underwater.
Until now, it was believed that all plants and animals use oxygen to produce adenosine triphosphate (ATP). This is a universal source of energy for all biochemical processes taking place in living systems. ATP generation from oxygen occurs in structures called mitochondria.
Each mitochondria has its own tiny genome in addition to the main one – in the cell nucleus. But when the researchers performed a genomic analysis of H. salminicola, they did not find mitochondrial DNA.
At first, the scientists decided that they had made some kind of mistake. However, further tests using a fluorescent dye that selectively binds to DNA confirmed the data.
The authors explain: although representatives of H. salminicola have organelles similar to mitochondria, they lack the genes responsible for respiration. In the body of the parasite, enzymes necessary for the production of ATP from oxygen are not produced.
Thus, H. salminicola is the first known multicellular one that can do without oxygen throughout its entire life cycle.
It remains unknown why the parasites lost their ability to breathe oxygen, but their immediate family did not. Probably, having reduced their genome, H. salminicola gained an important advantage: they thrive, reproducing as quickly and as often as possible, the authors of the research wrote.
In addition, it is unclear how this multicellular receives the necessary energy. Most likely, H. salminicola steals it from the host, the researchers suggest. Other similar parasites have proteins that help import ATP directly from infected animals. In the future, scientists intend to find out whether H. salminicola uses the same strategy.
We add that H. salminicola is harmless to humans, but it is a serious problem for fish farming, since it also parasitizes on commercial fish, for example, salmonids. Perhaps the new data will help experts understand how to protect fish from these strange parasites.