CONTACT CHEMOSTIMULI IN THE MATING-BEHAVIOR OF THE CATTLE TICK, BOOPHILUS-MICROPLUS

Mating of the cattle tick Boophilus microplus is mediated by chemical stimuli on the cuticle of females. Males are arrested on the dorsum of females attached to the host, frequently sample the substrate, and th en tip-over to the ventrally located gonopore. These behaviours are al so observed in vitro when males are placed on a small glass bead treat ed with a female extract. Time spent and tip-ever by male ticks on dum mies is used in an assay to test the behavioural significance of fract ions of the extract. TLC separation yields one apolar fraction that ar rests males, though much less so than the whole extract, but lost tip- over behaviour This apolar fi action contains a series of cholesteryl esters that, when tested individually, show no arrestment activity at levels present in the extract but, when combined, are as active as the fraction. When a small silica column is used for fractionation, all b iological activity is reproduced after recombining the fractions. In a ddition to the early eluting apolar fraction containing cholesteryl es ters, a set of highly active more polar fractions is isolated. Electro physiological recordings from gustatory sensilla on the pedipalps of m ale B. microplus, which are regularly brought into contact with the cu ticle of the female during mating, provide evidence for receptors in t wo of them responding to the whole extract and to the behaviourally ac tive polar fractions. Mating behaviour involving arrestment and tip-ov er is clearly initiated by a mixture of chemical stimuli, and tip-over behaviour is associated with the more polar material. Arch. Insect Bi ochem. Physiol. 39:65-80, 1998. (C) 1998 Wiley-Liss, Inc.