DOMESTIC CAT NOSE FUNCTIONS AS HIGHLY EFFICIENT GAS CHROMATOGRAPH, SAYS NEW STUDY

Scientists from Ohio State University and elsewhere have developed a 3D computer model of the nose of the domestic cat (Felis catus) and simulated how an inhalation of air containing common cat food odors would flow through the coiled structures.

They’ve found that the air separates into two flow streams, one that is cleansed and humidified and another delivering the odorant quickly and efficiently to the system responsible for smelling — the olfactory region. In essence, the study authors suggest, the cat nose functions as a highly efficient and dual-purposed gas chromatograph — a tool that, in the laboratory, detects and separates chemicals in vaporized form. In fact, the cat nose is so efficient at this that its structure could inspire improvements to the gas chromatographs in use today.

Domestic cats — one of the world’s most widely kept pets — possess a highly complex nasal cavity and a well-developed sense of smell, which plays important roles in feeding and social interactions.

They have high olfactory acuity and disturbance to the sense of smell may cause the cat to refuse food.

Terrestrial mammals usually have three sets of bone structure, called turbinates, in their nose: naso-, maxillary, and ethmoid turbinates.

In the cat, these turbinates are significantly more complex than in either humans or rodents and are comparable to those of the domestic dog.

The area of olfactory mucosa in the cat, housed mostly in the ethmoid turbinates toward the posterior end of the nose, is around 20 cm2, about four to five times that of humans and only twofold less than the average dog.

The complex nasal turbinate structure in the cat and the importance of its olfactory function to its survival provide an excellent model to examine the structure-function relationship.

Since the domestication of its ancestorб the African wild cat (Felis silvestris lybica), the domestic and feral cat has spread along with human settlements and thrives in various climates.

The complex nasal structure may be important for cats to adapt to these diverse environments.

“It’s a good design if you think about it,” said Ohio State University researcher Kai Zhao.

“For mammals, olfaction is very important in finding prey, identifying danger, finding food sources and tracking the environment.”

“In fact, a dog can take a sniff and know what has passed through — was it a friend or not?”

“That’s an amazing olfactory system — and I think potentially there have been different ways to evolve to enhance that.”

“By observing these flow patterns and analyzing details of these flows, we think they could be two different flow zones that serve two different purposes.”

In a new study, Dr. Zhao and colleagues developed an anatomically accurate 3D computational model of the nose of a domestic cat.

They drew on a variety of techniques, including high-resolution micro-CT scans of an actual cat’s nose and computational fluid dynamics modeling.

Simulation of air and odor flow through the virtual cat nose showed that it appears to function similarly to a parallel coiled gas chromatograph, in which the efficiency of the basic technique is boosted by the use of multiple tubes branching off of one high-speed gas stream.

In other words, if a cat’s nose only had one straight tube for odor detection, it would need to be longer than the physical size of the head allows in order for odor detection to be as efficient as it actually appears to be.

Having multiple complex channels appears to be 100 times more efficient than having a single straight tube — which most amphibians have.

These findings deepen understanding of how the evolution of more convoluted channels enabled mammals’ — especially cats’ — enhanced sense of smell.

“The evolutionary occurrence of the convoluted olfactory turbinate channels in mammalian noses, remarkably resembles a different sensory organ, the snail-like coiled cochlea that is also unique to mammals,” the researchers said.

“In birds and other non-mammalian vertebrates, the inner hearing organ, despite being called cochlea, is instead a blind-ended tube.”

“While we know that the evolution of mammalian cochlea enhances our hearing sensitivity and frequency range, we believe here that the mammalian olfactory cochlea may similarly enhance the sense of smell by serving as a parallel coiled chromatograph.”

“The finding reveals novel mechanisms to support high olfactory performance, furthering our understanding of the successful adaptation of mammalian species, including cat, an important pet, to diverse environments.”

The results appear in the journal PLoS Computational Biology.