ATTRACTANT-MEDIATED BEHAVIOR OF MOBILE STAGES OF HETERODERA-SCHACHTII

The responses of second-stage juveniles (J2) and males of Heterodera s chachtii to root exudates and female sex pheromonal substances, respec tively, at different distances from the attractant source, were studie d by analysing orientation tracks left on agarose surfaces. Two classe s of J2 were tested : stimulated J2, previously stimulated by root exu dates, and unstimulated J2. Track lengths were quantified to different iate between oriented and unoriented searching behaviour. The quantifi cation of forward movements towards and away from the gradient, subseq uent to each backward movement, enabled the differentiation of attract ant and repellent effects. Males showed no repellent responses. The co mparison of the sensory abilities between stimulated and unstimulated J2 points to the possible occurrence of ''learning'' processes.