How do the Na’vi people breathe?

Apart from the usual cellular respiration used also by living beings on earth, the Na’vi from the Avatar movie utilize an interesting chemical reaction that can be inferred even from the atmosphere alone.

Pandora’s atmosphere is made up of: nitrogen (50%), oxygen (25%), carbon dioxide (18%), xenon (5.5%), hydrogen sulphide (1%), methane and ammonia (0.5%). The last three gases are unbreathable by humans, and carbon dioxide is present in quantities too large for them to tolerate.

On an inhabited planet, it is difficult to find such a high percentage of a very reactive gas like CO2 without it playing some role in the physiology of the living beings. This has also been taken into account by the creators of the movies.

It seems that the Na’vi do in fact have special organs called ‘Wichow’ that take advantage of the high CO2 content to extract greater quantities of oxygen from the atmosphere.

These organs convert the CO2 and water inside their organisms into methane and oxygen. The former is exhaled and accumulates in the atmosphere (hence the small percentage of methane), while the latter is used for respiration.

When Pandora’s creatures rest or sleep, those same organs can convert the methane back into CO2 and water to hydrate themselves.

In short, they have an elaborate system for drawing more oxygen and water from the atmosphere, alternating between the two respiratory mechanisms in a way reminiscent of the way plants do on Earth.

This article is referred to in: Why bioluminescence?