According to the team's analysis, specialized cells in the fruit fly's primary taste organ, the labellum -- a structure on the fly's head that looks like a pair of lips covered in bristles -- respond to either sweet or bitter flavors, much like cells of the human tongue. However, while earlier work suggested mammalian bitter tasting cells are all alike, the Duke researchers found that different sets of bitter-sensitive nerve cells on the fly "tongue" bear distinct combinations of taste receptors, the Duke team found. Receptors are the protein switches that trigger the nerve cells to send signals to the brain's taste-processing centers in response to particular food items or other chemicals.
The unique coding of the flies' tasting cells raises the possibility that insects can discern among different bitter tastes more precisely than can humans or other mammals, said Hubert Amrein, Ph.D., assistant professor of genetics and lead author of the study. Amrein and his colleagues reported their findings in the June 22, 2004, issue of Current Biology. The work was supported by the National Institutes of Health.
"Our findings suggest that the sensory systems for taste in insects and mammals are set up in a remarkably similar manner, despite the fact that the structure of the taste organs are so different and that the genes involved bear no relationship to one another," Amrein said.
The fly's potentially more discriminating sensitivity to bitter tastes -- generally associated with unpalatable food or toxins -- might allow them to select the best food item among multiple suboptimal choices, Amrein
Contact: Kendall Morgan
Duke University Medical Center