Odor coding in the antenna of the tsetse flyGlossina morsitans

Abstract

Tsetse flies transmit trypanosomiasis to humans and livestock across much of sub-Saharan Africa. Tsetse are attracted by olfactory cues emanating from their hosts. However, remarkably little is known about the cellular basis of olfaction in tsetse. We have carried out a systematic physiological analysis of theGlossina morsitansantenna. We identify 7 functional classes of olfactory sensilla that respond to human or animal odorants, CO2, sex and alarm pheromones, or other odorants known to attract or repel tsetse. Sensilla differ in their response spectra, show both excitatory and inhibitory responses, and exhibit different response dynamics to different odor stimuli. We find striking differences between the functional organization of the tsetse fly antenna and that of the fruit flyDrosophila melanogaster. One morphological type of sensilla has a different function in the 2 species: Trichoid sensilla respond to pheromones inDrosophilabut respond to a wide diversity of compounds inG. morsitans.In contrast toDrosophila, all testedG. morsitanssensilla that show excitatory responses are excited by one odorant, 1-octen-3-ol, which is contained in host emanations. The response profiles of some classes of sensilla are distinct but strongly correlated, unlike the organization described in theDrosophilaantenna. Taken together, this study defines elements that likely mediate the attraction of tsetse to its hosts and that might be manipulated as a means of controlling the fly and the diseases it transmits.