Earlier this year we posted an article,( "All Animals are Aerobic - False "), which briefly mentioned the discovery of an anaerobic animal, called a loriciferan, at the bottom of the Mediterranean Sea. At first, this just seemed like one of the oddities of nature, an example of an organism that failed to read the textbooks on what its characteristics should be. For instead of oxygen, the energy-releasing molecule of the cellular respiration pathways, these loriciferans are hydrogen-based organisms, which utilize a structure called a hydrogenosome. Hydrogenosomes release hydrogen gas as a waste product, which may in turn be used by the cell to generate methane from carbon dioxide. The conversion of CO2 to releases a small amount of energy. Not the same as cellular respiration, but enough to power some cellular processes. 

 Nick Lane , biochemist and author of Oxygen:The Molecule That Shaped the World ", suggests that we should be taking a closer look at the anaerobic loriciferans and their hydrogen-based lifestyle. Current evolutionary thought follows that path that oxygen, the byproduct of photosynthesis, was the key molecule in the evolution of the eukaryotic organisms. Lane's article discusses an alternate hypothesis, that it was hydrogen that may have played an important role in the evolution of the eukaryotes.

The answer lies within the genetic information packed within the mitochondria and hydrogenosomes. By analyzing the DNA of aerobic and anaerobic organisms, and comparing it to the information found in anaerobic organisms with hydrogenosomes, it may be possible to determine whether hydrogen gas or oxygen gas was first step in the evolution of the eukaryotes. Either way, it seems as if there will have to be some revisions to the textbooks, and a retraction of the statement that all animals are anaerobes.

Additional Links

• Scientific Activist blogpost on ScienceBlogs
• New Scientist article "Genesis Revisited " (Aug 7, 2010) - subscription required