Exploration and Selection of Penetration Site By Tylenchida

Filmed observations of eleven tylenchid species show the same basic pattern of behaviour leading to feeding. Simple sequences of behaviour initiated in response to stimuli lead to egg-hatching and host penetration. Searching behaviour, stimulated chemically by a host, includes locomotion, head movements and probing with the stylet; this is called widespread exploration. In local exploration, when a surface has been encountered, locomotion stops and the surface is examined by lip rubbing and stylet probing. If found favourable, the surface is penetrated by repeated stylet thrusting, during which the body and head are immobile and the lips are pressed against the surface. On a food-cell feeding follows. In the cutting cycle, penetration by stylet thrusting alternates with very localised exploration and a slit is cut (e.g., in eggshell or plant-cell wall) through which the nematode then passes. Stimuli that initiate exploration, penetration and feeding, probably include surface contour, texture, deformability and chemical nature all sensed through labial tactors, muscle proprioceptors and amphids. But whether or not a response is made depends on physiological state. On this basis a scheme is presented that describes observed behaviour leading to feeding and provides a foundation for further behavioural studies.