Operculum

The operculum is a nostril-like opening found on many Pandoran fauna that is used to take in air for respiration. The more simian-like species on Pandora, such as the prolemuris have them; Na'vi, however, lack them, and breathe with nostrils, like many animals from Earth.

Description[]

Operculum are typically placed near the animal's neck or chest in either pairs or columns. They tend to be in close proximity to the lungs, allowing animals to breathe more efficiently. During intense movement (i.e. running or flying), air flows through the lungs in a continuous stream, providing a more active gas exchange, thus increasing efficiency. Despite the presence of this duct system, most animals tend to breathe in and out at rest, probably by closing the back openings with valves and allowing air to enter by expanding the chest. Since the animal's head is not directly involved in breathing, many Pandoran animals have a special muscular tube that conducts air to the vocal cords and allows them to make rather loud sounds.

Disadvantages[]

Despite the apparent advantages of operculum, there are some serious drawbacks.

It is not entirely clear how exactly Pandora's animals capture odors, however, if their olfactory organs are located at the level of the blowholes, then such a breathing system is extremely inconvenient for animals of small sizes. for example, viperwolves, due to their small stature, can lose their sense of smell in dense undergrowth , because of thick plants that filter out smells. However, larger animals in this situation can raise their heads above the vegetation, mitigating this disadvantage.
Operculum can be flooded with water when moving through wet areas, crossing water streams and entering the water, the animals are forced to close the blowholes with cartilaginous valves and breathe through the mouth. A similar problem can occur in thick dust or fog.
The ventilator system can work effectively only in warm climates: due to the lack of upper respiratory tracts to warm the air on the way to the lungs, animals can seriously freeze delicate tissues, rendering most Pandoran animals vulnerable in cold/glacial climates
The upper respiratory tract serves to decontaminate and filter incoming air, so most likely Pandora's animals have an additional filtration system at the entrance to the lungs.
Operculum are one of the few weak spots of an animal, as puncturing them with an arrow is likely guaranteed to kill the animal. The Na'vi utilize this weakness to great effect in the Great Hunt.

Trivia[]

In the early concept art of some animals, such as the Great Leonopteryx, there was only one operculum and it was a huge hole like an airplane air intake.