Context

Scientists at Tel Aviv University have discovered a jellyfish-like parasite that doesn’t need oxygen because it doesn’t breathe. Its life is entirely free of dependency on oxygen.

About

• The discovery was made by accident as the team was sequencing the genome of a common salmon parasite called Henneguyasalminicola.
• When they searched for a mitochondrial genome, they didn’t find anything.
• The discovery has enormous ramifications for not just one’s understanding of life on Earth, but also for astrobiology and one’s search for non-oxygen dependent life forms on other astronomical objects, possibly within the solar system. 

What is Mitochondria?

• Mitochondria are organelles that trap oxygen and help to break it down to provide energy for the cell.
• Mitochondria are membrane-bound cell organelles (mitochondrion, singular) that generate metabolic energy in eukaryotic cells needed to power the cell's biochemical reactions.
• Chemical energy produced by the mitochondria is stored in a small molecule called adenosine triphosphate (ATP).
• Mitochondria contain their small chromosomes. Generally, mitochondria, and therefore mitochondrial DNA, are inherited only from the mother.
  

What if, mitochondria are not present?

• The presence of mitochondria helps in harnessing oxygen and breaking it down for energy. Then, life took a dramatic turn and erupted.
• Unlike bacteria, all eukaryotic cells have mitochondria.
• Every cell in every plant or animal contains mitochondria, which generates fuel for the cell to burn and obtain energy.
• The lack of mitochondria implies that the animal does not use oxygen to function, as no other organelle or process in a cell is capable of breaking it down.
• It is not entirely known how the creature (parasite) obtains energy. It may be possible that it does so by absorbing molecules from the salmon that already produces energy.
• There are known organisms who have adapted to thrive in a low oxygen environment but until this study, whether there have been animals that don’t use oxygen has been a question that hadn’t been answered. 

Aerobic respiration: Aerobic respiration is a chemical reaction that transfers energy to cells. Plants and animals transport glucose and oxygen to tiny structures in their cells, called mitochondria. Here, glucose and oxygen take part in a chemical reaction. The reaction is called aerobic respiration, and it produces energy which transfers to the cells. The waste products of aerobic respiration are carbon dioxide and water.

The parasite

• Henneguyasalminicola is a myxozoan cnidarian — a type of animal-related to jellyfish and coral.
• It consists of less than 10 cells in its being. It lives inside salmon’s muscles and leeches energy off its host. But it is not a harmful parasite, it can live the fish’s entire life inside it.
• The environment inside its host is almost entirely free of oxygen. This meant that it didn’t need the mitochondria anymore once it found another way to adapt. So it dropped its mitochondrial genome entirely, so as to save energy and not copy genes for multiplication. It gave up breathing. 

Significance of the discovery:

• The discovery indicated that evolution can go in strange directions. It also brings into question the definition of ‘animal’ itself as breathing in oxygen is a part of it. 
• The findings indicate that there might be many more such animals to be found that counter our understanding of life.