Electropharyngeograms and stylet activity of second stage juveniles of Globodera rostochiensis

Analysis of the contraction and relaxation of pharyngeal musculature derives from measurements of electrical currents, termed electropharyngeograms (EPG). EPG of stylet protractor muscle activity of second stage juveniles (J2) of Globodera rostochiensis, in response to 0.1, 1.0 and 10 mg ml-1 concentrations of the neurotransmitter serotonin, have now been obtained and correlated with stylet protrusion and retraction using video analysis. The antagonist, gramine (10 mg ml-1), incorporated with 10 mg ml-1 serotonin, almost completely eliminated stylet thrusting by J2. Stylet movement can be determined accurately over extended periods with EPG and this approach has potential for investigating factors involved in activation and perturbation of stylet protrusion.