A team of researchers has discovered that mice can “smell” the level of oxygen in their environment. Mice have odorant receptor genes that allow them to detect oxygen concentrations. Although many animals have ways to detect molecular oxygen, this was the first recorded case of a mammal being able to sense oxygen by using their olfactory system. The details are in a paper that was just published in the journal Neuron.
The ability to find and detect oxygen is incredibly important to the survival of most mammalian species. A number of sensory mechanisms have evolved but scent had never been one of them. Mice have over 1000 odorant receptor genes. For comparison, humans have about 500-700 odorant receptor genes and our sense of smell is much weaker than that of a mouse.
Researchers from the Max Planck Research Unit for Neurogenetics collaborated with scientists from the University of Cambridge, the University of Saarland, and the Karolinska Institute in a large-scale study. The team found that mice had chemosensory neurons that responded to oxygen levels. Specifically, certain cells were activated when oxygen levels dropped, prompting the mice to move out of the area. The team identified two key genes for this mechanism–Gucyb12 and Trpc2. If these genes were deleted in laboratory mice, the mice couldn’t detect oxygen levels and would stay in low oxygen environments. The team speculates that this additional oxygen-sensing mechanism may have evolved because mic e live in burrows and need to be careful when monitoring oxygen levels. Mice need to be aware of which burrows have enough oxygen for the survival of their offspring, for example. This type of sensory mechanism for detecting oxygen has not yet been seen in other mammals.
The team’s findings show that mice have the ability to detect oxygen levels with their olfactory system. In other words, they can “smell” if oxygen levels are dropping to dangerous levels. This keeps them and their offspring safe in deep burrows.
Bleymehl et al. A Sensor for Low Environmental Oxygen in the Mouse Main Olfactory Epithelium. Neuron (2016).