Max-Planck Institut Seewiesen, 82319 Starnberg, Germany.
The two olfactory receptor neurons that innervate each trichoid sensillum on the antenna of the silk moth Bombyx mori comprise 60-65% of the total number of its olfactory cells. Although the responses of the males' trichoid sensilla to the female sex pheromone components bombykal and bombykol are well studied, comparatively little is known about the function of the females' trichoid sensilla. One of the two cells in each sensillum on the female responds strongly to benzoic acid and to benzaldehyde while the other responds strongly to 2,6-dimethyl- 5-hepten-2-ol and to linalool. As the silk moths do not feed during their adult life, it is likely that the females' trichoid sensilla mediate the search for oviposition sites near or on mulberry plants. Here we report an electrophysiological study on responses from females' trichoid sensilla to derivatives of 2,6-dimethyl-5- hepten-2-ol (henceforth called DMH) with more or with fewer carbon atoms than DMH, with the double bond in a different position or absent, and with the hydroxyl group replaced by a ketone or amine. The cells responded best (highest spiking rate) on stimulation with DMH though the threshold doses for DMH and linalool, which has an extra carbon double-bonded to C1 of DMH, were the same. All other derivatives of DMH elicited lower or no responses. Although linalool has been identified in extracts from mulberry, air from a bottle containing mulberry (leafed branches, crushed leaves, or foliage upon which Bombyx larvae have fed) does not elicit spike responses from the linalool-sensitive cell.