7/13/2010

One thing that I have found most annoying about the movie Avatar is the chorus of praise for its "scientific accuracy." I don't know of any movie short of Star Trek that has tried so hard to convince its fans that it's based on real science, and fallen so short. So I thought it would be useful to just make an archive showing that the movie is not science-fiction; it's science mixed with fantasy. This week, we'll look at another odd biological design, chest nostrils.

Many of the creatures on Pandora like the Direhorse and the Mountain Banshee have nostrils on their chests instead of their heads. These holes are officially called "spiracles" in the Avatar universe. Air is driven through the front holes and blown out of gills in the back. One article suggested this was a good idea, since having the lungs and the stomach connected by the throat can cause choking. I disagree entirely. No animals on Earth have a breathing system anything like the Pandoran system, and there's a good reason for it.

The elongated throat serves as a barrier to protect the lungs. Nothing can get to the lungs without going through the nostrils and throat, and the throat is long enough to serve as a protection. If the organism breathes in cold and dry air, then the throat warms and moisturizes it. If the organism breathes in hot and moist air, then the throat cools and slightly dehydrates it. If debris is inhaled, then it will most likely get caught and trapped in the throat before it reaches the lungs. If germs or bacteria are inhaled, they'll more likely than not to get trapped in the lining of the throat to prevent them from reaching the lungs. There's another good reason why we have our nostrils on our heads. Having the nostrils that high on the body also minimizes the risk of drowning.

Now let's look at the "spiracles." With the lungs right behind the nostrils in the chest, that means there's a shorter distance between the lungs and the outside world. Any mud or dirt thrown up by the running Direhorse could fly directly into the lungs. If the Direhouse ran through a deep puddle, it could choke. If the Direhorse went into water even chest-deep, it could drown. The only way to prevent this would be to close up the spiracles, which would mean the animal wouldn't be able to breathe when it was in water or a dusty area. Even without those extreme scenarios, the risk of infection is also increased since any germs or bacteria would right into the lungs. The lungs could also dry out easily since there's no throat to warm or moisturize the air.

Ultimately, it goes down to whether there's any real benefit to putting nostrils on the chest. I don't really see a point to it. Apparently, the real reason for the spiracles was that James Cameron wanted the animals modeled after race cars. The spiracles are supposed to mimic car's intake vents. Once again, Cameron threw logic out the window to create something "cool." Which is, of course, flawed science.

What do you think of Avatar's spiracles?

6 comments:

Trantor2nd said...

The point is that Pandorans evolved differently as compared to Terrans. Spiracles may be less efficient but are not illogical. All your astute reasoning doesn't answer why your nostrils are not high up on top of your head. You might as well question why the Na'vi are blue.

Maurice Mitchell said...

Sounds like the sequel to Speed Racer LOL

Anonymous said...

Race cars? I hope that isn't true. Since when does nature mimic technology? It's supposed to be the other way around.

Still funny, though. Six-limbed race cars...IN SPACE.

Nigel Mitchell said...

Sad to say, it is true. If you check the link associated with the statement, you'll find an interview with one of the movie's production designers. He explains how Cameron wanted the creatures to be like race cars...hence the chest nostrils

Arzenjo said...

Sorry bro, but all terrestrial arthropods have a similar system. They all have Malpighian tubes, that serve as air exchange conducts. These are located on the sides of their bodies, it is a design far more successful than the tetrapod formula of nostrils on the head. Why? Because they hardly get sick from their respiratory apparatus, because it is far simpler to keep clean and with far less water expenditure.

Cheers from Mexico

Biologist said...

It's not flawed science. You are simply too earth-centric in your thinking. You are assuming their lungs are as susceptible as ours to water. You are also assuming the spiracles are simply nostrils while they could be as complex as our own throats. Can you swim under water with your mouth open and not drown? I can. The trachea is a direct path to our lungs, but we have the larynx and epiglottis to block water from rushing in. Whales have blow-holes, but do you think they drown? As to no being able to breathe in chest-high water, you assume the spiracles are the only path to the lungs(or something like the lungs). We see the creatures on Pandora breathing and vocalizing from their mouths, which requires air from their lungs. Much like our own nose and mouth, if one is blocked, we can breath through the other.

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