ANTENNAL PERCEPTION OF OILSEED RAPE, BRASSICA-NAPUS (BRASSICACEAE), VOLATILES BY THE CABBAGE SEED WEEVIL CEUTORHYNCHUS-ASSIMILIS (COLEOPTERA, CURCULIONIDAE)

The response of the Ceutorhynchus assimilis antenna to volatiles in ai r entrainment-derived extracts of oilseed rape, Brassica napus, was st udied using coupled gas chromatography (GC)-electroantennography (EAG) and coupled GC-single cell recording (SCR). By means of these techniq ues and coupled gas chromatography-mass spectrometry (GC-MS). 25 activ e compounds were identified, including isoprenoids and compounds deriv ed from fatty acids and amino acids. Some of the latter, the isothiocy anates and goitrin, and probably indole and benzyl cyanide, are catabo lites of glucosinolates. The electrophysiological activity of the iden tified compounds was confirmed by EAG using a physiologically discrimi nating dose, and by SCR studies. The importance of the combined use of the EAG and SCR techniques was demonstrated, since specific olfactory cells were located for five compounds that did not elicit significant EAG responses. The majority of the olfactory cells from which single cell recordings were obtained showed very high specificity, and in num erous recordings there were consistent pairings of specific cell types .