African Elephants have the Largest Number of Olfactory Genes

Researchers reveal that African elephants have the largest number of olfactory genes - twice of that found in dogs and five times more than that in humans.

For many animals, the sense of smell is very critical for survival. It is the number of olfactory receptors present in the organism's genome that helps them sniff food and avoid predators. It is the sense of smell that helps them find mates.

In the new study, researchers at the Cold Spring Harbor Laboratory, examined the olfactory receptor (OR) repertoire from 13 mammalian species. They saw that African elephants had the Largest number of OR genes.

The researchers characterize the capabilities of olfactory in different mammals, for which they examined the genome sequences from 13 placental mammals and identified more than 10,000 OR genes on the whole. They noticed that the African elephants had the most extensive olfactory repertoire with 2,000 OR genes. 

"The functions of these genes are not well known, but they are likely important for the living environment of African elephants," said author Yoshihito Niimura. "Apparently, an elephant's nose is not only long but also superior." 

On the other hand, it was humans, along with other primate relatives, that had lesser number of OR genes when compared to other species that were examined. 

The evolutionary histories of OR genes was traced using a new computational tool that was used to extract the ancestral genes. They then examined the duplication or loss in each species. In some species, the few lineages of the OR genes expanded in a given species. This was seen in elephants where the ancestral genes duplicated in elephants generating 84 distinct genes.

"Comparison of the repertoires of OR genes among mammals lets us know the commonalities and differences of olfactory perception, deepening our understanding of the sense of smell in humans," Niimura said.

The finding was documented in Genome Res.