Buried in the nose of Fuggles the mouse lemur are specialized pheromone receptors that help her distinguish friend from foe in the dark of night, when mouse lemurs are active.
By Robin Ann Smith
If you could pick one superpower, consider taking inspiration from lemurs. Some lemurs can safely digest cyanide in amounts that would kill an elephant. Others can enter hibernation-like states to survive periods when food and water are in short supply. Still others have keen powers of scent, with the ability to find mates and avoid enemies in the darkness by smell alone.
Research by biologist and Duke Lemur Center director Anne Yoder suggests that the molecular machinery for sniffing out pheromones — much of which has gone defunct in humans and many other primates — is still alive and well in lemurs and lorises, our distant primate cousins.
Lemurs use scents to mark the boundaries of their territories, distinguish males from females and figure out whether another animal is friend or foe. When a lemur gets a whiff of another animal, specialized pheromone receptors in the lining of the nose transmit the information to the brain, triggering instinctive urges like mating, defense and avoiding predators.
The receptors are proteins encoded by a family of genes called V1Rs. First identified in rats in the mid-1990s, V1R genes are found in animals ranging from lampreys to humans. But the proportion of these pheromone-detection genes that actually functions varies greatly from one species to the next, Yoder said last week in a roundtable discussion hosted by Duke’s Science & Society program.
Randy the ring-tailed lemur scent-marks his territory. Photo by David Haring.
Studies suggest that as much as 90% to 100% of the pheromone-detection genes in humans consist of disabled pieces of DNA, called pseudogenes.
“Our pheromone-detection genes are so boring — we don’t have many of them, and almost all of them are broken,” Yoder said.
But in lemurs and lorises — whose ancestors split off from the rest of the primate family tree more than 60 million years ago — the proportion of pheromone-detection genes that is still intact is much higher.
In a study published this year, Yoder and colleagues analyzed the DNA of 19 species and subspecies of lemurs and lorises, looking for subtle differences in their V1R genes. They found that one group — the mouse lemurs — has the highest proportion of intact V1R sequences of any mammal yet studied.
To find out which genes are linked to which scents, Yoder and her colleagues plan to take DNA sequences from pheromone-detecting genes in lemurs, insert them into mice, and expose the mice to different scents to see how they respond.
An ability to sniff out the right mates — and avoid being seduced by the wrong suitors — may have served as a mating barrier that allowed lemur species to diverge after arriving in their island home of Madagascar, helping to explain how the more than 70 living species of lemurs came to be, Yoder says.