IDENTIFICATION OF VERTEBRATE VOLATILES STIMULATING OLFACTORY RECEPTORS ON TARSUS-I OF THE TICK AMBLYOMMA-VARIEGATUM FABRICIUS (IXODIDAE) .2. RECEPTORS OUTSIDE THE HALLERS ORGAN CAPSULE

Bovine odour excites olfactory receptor(s) in a wall-pore olfactory se nsillum on the anterior pit of Haller's organ in Amblyomma variegatum. Gas chromatography-coupled electrophysiology recordings from this sen sillum reveal the presence of 4 active compounds in bovine odour. The two strongest stimulants were identified as 2-nitrophenol and 4-methyl -2-nitrophenol by gas chromatography-coupled mass spectrometry, and by matching electrophysiological activity of synthetic analogues. Synthe tic analogues of known vertebrate-associated volatiles also stimulate other olfactory receptors in sensilla on the surface of tarsus I: a la ctone receptor responding to gamma-valerolactone and 6-caprolactone; d ifferent fatty acid receptor types responding best to either pentanoic acid, 2-methylpropanoic acid or to butanoic acid; three receptors res ponding to NH3; and one receptor responding to 3-pentanone. Gas chroma tography-coupled mass spectrometry analysis of vertebrate volatiles re vealed presence of a number of these olfactory stimulants in concentra tes of rabbit and steer odour, i.e. 2-methylpropanoic acid, butanoic a cid, 3-methylbutanoic acid, pentanoic acid, and gamma-valerolactone.