Analysis of the sensory responses of parasitic nematodes using electrophysiology

Use of the electrophysiological technique to examine the sensor?; perceptio n of live, intact nematodes has provided detailed analysis of responses to known concentrations of test chemicals. The use of larger nematodes, such a s the animal-parasite Syngamus trachea, enabled direct extracellular record ings from individual sensilla: with smaller nematodes, the recording electr ode was inserted close to the cephalic region. Extracellular recordings fro m the cephalic region of second-stage juveniles and males of the potato cys t nematodes, Globodera rostochiensis and Globodera pallida, were obtained a fter exposure to a variety of semiochemicals. including sex pheromones and certain putative phagostimulatory compounds, The responses of adult females of the animal-parasitic nematode, Brugia pahangi. to some possible host cu es, and the inhibition by ivermectin of the response to a known allelochemi cal were investigated. Exposure to acetylcholine was used to compare the co ncentration-dependent responses of second-stage juveniles of C. rostochiens is and adult females of B. pahangi and the insect-parasitic nematode Leidyn ema appendiculata. Use of a perfusion system enabled sequential exposure of individual nematodes to different test chemicals or to different concentra tions of the same chemical. incubating second-stage juveniles of G. rostoch iensis for 24 h in a mAb showing specificity to amphidial secretions result ed in blocking of the normal response to host root diffusates. The potentia l of the electrophysiology technique for analysing perturbation of sensory perception is discussed. (C) 2001 Australian Society for Parasitology Inc. Published by Elsevier Science Ltd. All rights reserved.