(A work in progress)
A taxis is directed movement of an organism towards or away from a stimulus. A kinesis is a change in the rate of activity, or frequency of turning of an organism in the presence of a stimulus. Reduced activity or more frequent turning can result in aggregation near the stimulus. Resource-locating behavior in nematodes probably consists of a combination of taxes and kineses (Lee, 2002; Rodger, 2003; Young et al, 1998).
Taxes and kineses are characterized according to the nature of the stimulus. Thus, chemotaxis is a directed response to a chemical gradient; thermokinesis is a change in movement pattern in relation to temperature.
Although it has been known for many years that nematodes are attracted to plant roots (Prot, 1977; Prot and Van Gundy, 1980) and root exudates (Riddle and Bird, 1985; Viglierchio, 1961), no uniquely plant-derived compounds that might produce these responses have been identified. Carbon dioxide, expected to be in higher concentrations in the rhizosphere than in bulk soil is a strong attractant in a certain concentration range (Klingler, 1965; Pline and Dusenbery, 1987; Robinson, 1995).
Tracks of Heterodera schachtii J2 in relation to a Plant Root
Photograph by J. Aumann, NemaPix.
Interestingly, given the choice of plant roots and insect larvae in an olfactory tube, bacteriophagous entomophilic nematodes moved to plant roots (Boff et al, 2002), however, prior to invading the host, nematodes must sense additional factors to differentiate between the sources of general signals (Ruhm et al, 2003). CO2 may provide a directional stimulus and stimulate a taxis response. However, once the nematode is near the resource, plant signature compounds, such as flavonoids or alkaloids, may precipitate kinesis responses resulting in localization of individuals around food sources.
Attraction or repellency of host plants to nematodes has been the subject of several investigations, but only a few host- or nonhost-specific compounds mediating this attraction are known (Chitwood, 2002). Maize roots exude cyclic hydroxamic acids, one of which (2,-4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one) attracts Pratylenchus zeae at concentrations in host exudates.
Boff MIC, van Tol RHWM, Smits PH. 2002. Behavioural response of Heterorhabditis megidis towards plant roots and insect larvae. Biocontrol. 47:67-83.
Chitwood D.J. 2002 Phytochemical based strategies for nematode control. Annual Review of Phytopathology 40:221-249.
Friebe A, Klever W, Sikora R, Schnabl H. 1998. Allelochemicals in root exudates of maize: effects on root lesion nematode Pratylenchus zeae. See Ref. 133A, pp. 71-93 45. .
Fu, S, Ferris, H., Brown, D, Plant, R. submitted Does "bacterial-farming", a positive feedback of nematodes on their bacteria prey vary with nematode species and population density? Soil Biology and Biochemistry.
Fukuzawa A, Furusaki A, Ikura M, Masamune T. 1985. Glycinoeclepin A, a natural hatching stimulus for the soybean cyst nematode. J. Chem. Soc. Chem. Commun. 1985:222-224, 748 46. . Gheysen G. 1998. Chemical signals in the plant-nematode interaction. See Ref. 133A, pp. 95-117
Klingler, J. 1965. On the orientation of plant nematodes and of some other soil animals. Nematologica 11:14-18.
Lee, DL. 2002. Behavior. Pp369-387 in DL Lee (ed) The Biology of Nematodes. Taylor and Francis, London.635p.
Perry RN. 1996. Chemoreception in plant-parasitic nematodes. Annu. Rev. Phytopathol. 34:181-89
Perry, RN 1996. Chemoreception in plant parasitic nematodes. Annual Review of Plant Pathology. 34:181-199.
Phillips DA, Ferris H, Cook DR, Strong DR. 2003. Molecular control points in rhizosphere food webs. Ecology 84: 816-26
Pline, M., and D.B. Dusenbery. 1987. Responses of the plant-parasitic nematode Meloidogyne incognita to carbon dioxide determined by video camera-computer tracking. J. Chem. Ecol. 13:873-888.
Prot J-C, Van Gundy, SD. 1980. Effects of soil texture and the clay component on migration of Meloidogyne incognita second-stage juveniles. Journal of Nematology 13:213-217.
Prot J-C. 1977. Amplitude et cinétique des migrations du nématode Meloidogyne javanica sous l'influence d'un plant de tomate. Cahiers ORSTOM Sér Biol. 11:157-166.
Riddle, D.L. and A.F. Bird, 1985. Responses of the plant parasitic nematodes Rotylenchus reniformis, Anguina argostis and Meloidogyne javanica to chemical attractants. Parasitology 91:185-195.
Robinson, AF. 1995. Optimal release rates for attracting Meloidogyne incognita, Rotylenchulus reniformis, and other nematodes to carbon dioxide in sand. Journal of Nematology 27:42-50.
Rodger S, Bengough AG, Griffiths BS, Stubbs V, Young IM. 2003. Does the presence of detached root border cells of Zea mays alter the activity of the pathogenic nematode Meloidogyne incognita? Phytopathology 93:1111-1114.
Romeo JT, Downum KR, Verporte R, eds. 1998. Phytochemical Signals and Plant-Microbe Interactions. New York: Plenum
Ruhm R, Dietsche E, Harloff HJ, Lieb M, Franke S, Aumann J .2003. Characterisation and partial purification of a white mustard kairomone that attracts the beet cyst nematode, Heterodera schachtii. Nematology 5:17-22.
Trett, MW, Perry RN 1985 Functional and evolutionary implications of the anterior sensory anatomy of species of rooy lesion nematodes (genus Pratylenchus). Revue de Nematologie 8:341-355.
Van Tol RWHM, van der Sommen ATC, Boff MIC, van Bezooijen J, Sabelis MW, Smits PH. 2001. Plants protect their roots by alerting the enemies of grubs. Ecology Letters 4:292-294.
Viglierchio, D.R. 1961. Attraction of parasitic nematodes by plant root emanations. Phytopathol. 51:136-142
Ware, R.W. D. Clark, K. Crossland, R.L. Russell.. 1975. The nerve ring of the nematode Caenorhabditis elegans: sensory input and motor output. J. Comp. Neurol. (1975) 162: 71-110
Young IM, Griffiths BS, Robertson WM, McNicol JW. 1998. Nematode (Caenorhabditis elegans) movement in sand as affected by particle size, moisture and the presence of bacteria (Escherichia coli). European Journal of Soil Science 49:237-241.
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