Flies That Can’t Smell just Can’t Tell

Just how important is a good sense of smell in matters of romance? Well, for male fruit flies, it’s so vital that the absence of just a single olfactory gene renders them as indiscriminate in matters of courtship as my cousin Freddie (no offense, Freddie).

Scientists at Duke University Medical Center have found that male fruit flies without the gene Gr32a, a critical pheromone receptor, were sexually outperformed by four to one in comparison with normal male competitors. They also tended to court females which had been doused with male pheromones, behavior not observed in normal fruit flies because females which smell of male pheromones have presumably already mated. In fact, the hapless Gr32a-impaired flies were just as happy to court the male competitors themselves.

So important are the signals from this single pheromone receptor that they are wired directly into the higher-order processing center of the fly’s brain, which governs behavior. “It goes against the dogma that was established for the olfactory and taste systems,” said Hubert Amrein, Ph.D., of the Duke Department of Molecular Genetics and Microbiology. “Our finding implies that signals from the outside don’t have to go through processing stations in the chemosensory system before being connected to the higher-order brain structures.”