Host Finding by Plant-parasitic Nematodes

Soil and Plant Interactions’ 5

Impact on Plant-parasitic

Nematode Host Finding and

Recognition

A. Forest Robinson

USDA-ARS, Southern Crops Research Laboratory, 2765 F&B Road,

College Station, TX 77845, USA

Introduction

Our understanding of host finding and recognition by plant-parasitic

nematodes is limited. Since plant-parasitic nematodes share morphology,

ancestry, niches and behaviour with other nematode species, it is

important to examine what is known regarding them as well.

I shall focus this review on nematode locomotion. Croll and Sukhdeo

(1981), however, list more than 20 kinds of nematode movement in

addition to locomotion, ranging from isolated to coordinated repetitive

motions and complex sequences of actions. Control of various internal or

supporting muscles attached to the oesophagus, stoma and reproductive

apparatus is involved during feeding, copulation, oviposition, defecation

and perforation of barriers during hatching, skin penetration and tissue

migrations.

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 move-

ment 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-

CABInternational2002.The Behavioural Ecology of Parasites
(eds E.E. Lewis, J.F. Campbell and M.V.K. Sukhdeo) 89