Orientation of male <i>Heterodera rostochiensis</i> Woll. and <i>H. schachtii</i> Schm. to their females

Abstract

SUMMARY A chemical attractive to their males is emitted by females of Heterodera rostochiensis and H. schachtii. The attraction is evident in agar plates when the females have been killed or removed from the agar, and on 3 mm. thick agar it takes more than 15 min. at 20° C. to diffuse sufficiently to be perceptible to males 5 mm. from the females. The perception is gustatory and seems to elicit klinokinetic aggregation behaviour and klinotaxic orientation. The males respond to a decrease in stimulation by stopping, followed by either a reversal and turn, or a swing and turn. Fatigue of the receptors, leading to loss of acuity of perception, occurs at greater concentrations of the attractant and decreases the frequency of turning. Then the intensity of turning increases and the approach to the female is less well orientated. Females of H. schachtii secreted a less labile or more concentrated attractant; thus their males were more frequently less well orientated and removal of the females caused more direct attraction. Male behaviour was efficient enough to ensure mating even of isolated females.