Definitions

The behavioural terminology adopted here is that proposed by Burr (1984) and adopted by Dusenbery (1992). The most important concepts for nematodes are migration, taxis and kinesis. Migration is the net movement of an individual or population in response to a stimulus gradient and can be accomplished by taxis or kinesis. Taxis is migration achieved by directed turns, which orientate the body axis relative to the gradient, whereas kinesis is migration achieved by undirected responses, such as by altering the rate of movement (orthokinesis) or incidence of random turning (klinokinesis) when going up or down a gradient. Taxis and kinesis are root words to which prefixes are often added. Prefixes that have been used for operative stimuli affecting nematodes include chemo-

┬ęCAB International 2002. The Behavioural Ecology of Parasites

(eds E.E. Lewis, J.F. Campbell and M.V.K. Sukhdeo) 89

(chemical), galvano- (electric field), geo- (gravity), magneto- (magnetic field), photo- (light), rheo- (fluid flow), thermo- (temperature) and thigmo-(touch). Other environmental variables shown or proposed to influence directional movement by nematodes include electric current, osmotic pressure, pH, redox potential, soil moisture, surface tension and soil texture.

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