Plant Nematology

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Department of Plant Pathology

3. Presentation on
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4. Nematode Behaviour
Nematode Movement
Movement of nematode in Egg
Factors influencing the nematode movement
Movement of nematode in Soil and Root
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Movement of nematode after hatching
Conclusion

5. Integration of sensory and motor inputs
“Neuromuscularly controlled movements of the nematode body or its parts”
(i) Travel or rotation of the nematode through space (locomotion)
(ii) Events of physiological or developmental importance
(hatching, feeding, copulation, egg laying, defecation, root penetration)
(iii) Postures or integrated movements of groups of nematodes
(coiling, clumping, swarming and nictating) enhancing survival and phoresis.
COILING SWARMINGCLUMPINGLOCOMOTION PENETRATION
Results in:
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6. Survival of animals is their ability to disperse and migrate in order to find
a habitat in which their physiological characteristics can function best
Facts…..
Survival depends on the capability
to disperse and migrate
locate and catch their food, and to find
a mate
Free living nematode moves faster
than plant parasitic nematodes
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7. Nematode move by undulating propulsion.
A train of dorso ventral waves passed from the head
to tail.
The waves are formed by the coordinated
contraction and relaxation of the longitudinal
muscles on the dorsal and ventral side of the body.
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8.  Locomotion in nematodes involves somatic muscles that are present
below the cuticle and hypodermis.
 During locomotion the muscles are used to apply pressure laterally to the
cuticle, this pressure is opposed by the high hydrostatic pressure of the
coelom and causes dorso-ventral bending.
 These muscular contractions cause the nematode moves in a 'sinusoidal'
manner.
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9. (a) Dorsal muscles relax, ventral muscles contract
(b) Dorsal muscles begin to contract, ventral muscles to
relax
(c) Dorsal muscles are now contracted and ventral
muscles relaxed.
♣ During undulatory movement waves are passed along the body in a direction opposite to
that in which the nematode is moving, relative to the ground.
♣ Thus, as the nematode moves forward the waves pass backward and, on reversing, the
waves travel forward
FIG. 1. The progressive change in form and curvature of a segment ABCD as the nematode
moves to the right
Dorsal
Ventral
Bcz, of their morphological simplicity and lack of appendages, can exert a force against external objects in
only one way, by undulatory propulsion
Potential energy in nematode muscles
Kinetic energy
Muscles must contract
Body bends
Wallace, 1986 9

10. HOW
In all such activities
the nematode has to
push backwards
against external
resistances in order
to exert force in a
forward direction.
How does a nematode propel itself
around in the egg before hatching?
How does it vacate the egg?
How does it migrate
through the soil pore
spaces and through thin
water films?
How does it penetrate the host?
How does it move
through the host's
tissues?
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11.  The locomotion of nematodes in any environment, or the exertion of pressure against
barriers such as the egg shell during hatching, or the epidermis of the root during
feeding or invasion, are thus basically the same process.
 The pattern of this behaviour may vary according to the environment, and, although
the end results may be very different, the mechanism is the same
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12. MOVEMENT IN THE EGG AND HATCHING
֍ Movement of a nematode within the egg appears at first to bear little relation to
undulatory propulsion.
֍ Waves are transmitted along the body, however, meet external resistances just as in
locomotion through the soil.
֍ During movement in the egg each part of the body is constantly changing form, and the
egg shell provides the external resistance necessary for Propulsion.
֍ The nematode moves very actively within the egg shell prior to hatching, by applying
increased pressure at the ends, increases the volume of the egg. Wallace, 1986
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13. (a) a single S-curve;
(b) 3 S-curves ;
(c)a three-dimensional array of S-curves.
The S-curve is the basic unit of propulsion.
 Pressure applied by the nematode at either end of the
egg (B, E) is opposed by equal and opposite reactions
R1 and R2, which can each be resolved into two
forces, a propulsive force (PI, P2) and a distortion
force (S1, S2).
 For gliding motion in the egg at constant speed, S1 is
equal and opposite to S2, and PI and P2 equal the
friction forces F1 and F2, respectively
Wallace, 1986
FIG.2 Dynamics of nematode movement within the egg.
FIG.3 Patterns of coiling in the egg shell
Eggshellnematode
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14. ⸙ The nematode enters an environment, after hatching from the egg, the nature of
which depends on the particular life cycle.
⸙ Free-living nematodes and the free-living stages of parasitic nematodes occur
commonly in the
i. soil
ii. water films on the surface of plants
iii. deep fresh or salt water.
⸙ Some species hatch within the plant or animal host, and consequently they have to
migrate through the tissues or through spaces such as the gut or blood vessels.
Wallace, 1968
soil
Movement of nematodes after Hatch
Plants Hatch within the plants14

15.  Soil pore spaces, size depends on the size
of the soil crumbs.
 There is little disturbance of the crumbs
during locomotion except in water-
saturated soils.
 A nematode moving along a sinusoidal
track through soil particles shows a
progressive change in curvature along its
length.
Single propulsive unit
Tension is developed in
the muscles on that side.
Soil particles
 Each half-wave operates as a single propulsive unit, successive half-waves being
propelled by tension developed in muscles on opposite sides of the body.
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16. 360 ̊
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17. Chemosensilla Mechanosensilla
Semiochemicals: interaction between organisms
♣ Alleolochemicals: Volatile or non-volatile toxic
chemicals
♣ Pheromones: Intraspecific responses, produces
in order to attract other organisms.
Sex pheromones, aggregation pheromones,
alarm pheromones or host marking
pheromones.
♣ Terminates beneath the cuticle
surface and ducts involved in
locomotion and external stimuli
(temperature, CO2, plant secretions,
salts)
♣ Expressed at the cuticle surface as
raised areas or bumps, papillae
Perry (2005)
Types
Video :2. Chemosensilla Video :3. Mechanosensilla 17
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18. Chemotaxis can take plant-parasitic nematodes to the source of a chemo-
attractant via the shortest possible routes.
(Andy et al., 2010)
(i) All of the air-filled
channels are
accessible to the
nematodes
(i) Nematodes can
resolve all chemical
gradients no matter
how small.
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Attraction of M. incognita & M. graminicola towards the roots of
different host plants in a designed path
Nematodes
Modified Y-chamber
(Andy et al., 2010)
Nematode behavior is studied in the
simplest kind of lattice consisting of
a modified Y-chamber olfactometer
in which there are just two routes to
a plant root, one long and one short.
Nematodes are always predicted to
take the shortest, most direct route to
the source of a chemo-attractant
Pluronic gel.

20. Physical factors influencing occurrence and rate of
movement
Temperature, oxygen availability, toxins , ionic status and water
Soil is particulate and small pores to permit nematode movement
Porosity varies with the size of soil particle and soil compaction
All nematode require a film of moisture of a certain thickness for movement
Nematode occupy interstices
completely filled with water
Nematodes occupy pores filled
only partly with water
(Yeast, 2004)
Interstitial Pellicle
Nematodes
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21. 1. Orientation to Temperature
 Nematodes locate the plant roots via thermal gradient preferably
heat produced during metabolism of roots and rhizosphere
bacteria (Sherif, 1969)
Sensitivity to temperature
Most Plant parasitic nematode(PPN) become inactive between
5 - 15⁰C and 30 - 40⁰C
Optimum range for activity is between 15 to 30⁰
Temperatures below 5 and above 40⁰C are often lethal
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22. 2. Chemicals
 Stimuli may attract or repel nematodes towards or away from
roots
 Chemicals may be CO₂, root exudates or salts; CO₂ is
considered as a principle attractant.
 Most attractive part of the roots is believed to be the tip / zone
of elongation and root hairs
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Fig : 7. Nematode penetration at the
zone of root elongation
Fig : 8. Nematode penetration near
the root tip 22

23. Table: 1. Preferential zones of penetration and aggregation
of PPN on roots
(Prot, 1980) 2323

24.  CO2 – strong attractant to a number of species and most
common and potent nematode attractant in a nature.
 It is released abundantly in living and decaying plants,
providing an cue to the possible presence of food.
Plant-parasitic nematodes attracted to CO2
Aphelenchoides fragariae; Bursaphelenchus xylophilus; Ditylenchus
dipsaci; Heterodera schachtii; Meloidogyne hapla; M. incognita; M.
javanica; Pratylenchus neglectus; P. penetrans; Rotylenchulus reniformis
(Perry et al., 2004)
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25. J2s nematodes in soil, recognize the signals emanating from host plants
using a complex array of chemosensory neurons, amphids were the sense
organs through which nematodes responded to the stimuli and establish a
permanent feeding site. (Bird, 2004; Cortese et al., 2006)
Ex: Allelochemical diffusate from the roots
of potato attracts Globodera rostochinensis.
The spike of egg hatching activity and J2 of
G. rostochinensis increased when exposure
to potato root diffusate (PRD)
(Perry et al. 2004).
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(Andy et al., 2010 UK)
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26. 2iii. Salts
 Most of the salts present in soil repel nematodes
Eg: second- stage juveniles of Meloidogyne spp
 Attracts free-living nematodes Eg: C. elegans
 Role: serve as a collimating stimulus or help nematodes to
find an appropriate soil depth
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27. IAA
• Induce the production of nematode secretions
• Increase in nematode mobility
Molecules present in root exudates, including IAA may act as
environmental signals to induce these behavioral changes
and therefore play a vital role in the host-recognition
processes for sedentary plant parasitic nematodes.
BELOWGROUND CHEMICAL COMMUNICATION:
ROOT EXUDATES AND HOST RECOGNITION
Curtis, 200827

28. The preferred site for root
invasion is at the elongation
zone of growing tips where
higher levels of IAA fluxes
have been recorded
Transport of IAA in plants
occurs from the shoot to the
root tip and then laterally to
the epidermis
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29. MOVEMENT OVER GREAT DISTANCES
• Dissemination by wind, irrigation, flooding, active man and animal
• Evidences shows that major means of movement is passive .
• Moves a few cm per year
• Nematodes could also follow the growth of the roots on which they are feeding,
as observed by Radopholus similis spread up to 15 m per year in a citrus
grove.
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30. Evidence indicates, that, unless carried passively, plant parasitic nematodes usually
spend most of their life in the vicinity of their birth, moving perhaps only a few
centimeters a year.
However,
 Ditylenchus dipsaci migrated 10 cm within 5 h in a temperature gradient.
Wallace (1961)
 The males of Globodera rostochiensis migrated 15 cm in 72 h to reach females
Evans (1969-1970)
 Some juveniles of the same nematode were able to migrate successfully 45 cm to
reach the host plant roots (Rode, 1962) and 40 cm in a temperature gradient (Rode,
1969).
Anguina tritici could travel upwards in the soil of 30 cm in order to parasitize’ wheat
plants
(Leulcel, 1962)
 Santos (1973) observed that males of Meloidogyne spp. were capable of moving 15 cm
in the absence of any stimulus.
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Conclusion
 Survival of animals is their ability to disperse and migrate in order to find a habitat in
which their physiological characteristics can function best-locate and catch their food,
and to find a mate
 Behaviour of nematode mainly involves integration of sensory and motor inputs
 Nematode move by undulating propulsion. A train of dorso ventral waves passed
from the head to tail.
 The muscular contractions cause the nematode moves in a 'sinusoidal' manner.
 The locomotion of nematodes in any environment, or the exertion of pressure against
barriers such as the egg shell during hatching, or the epidermis of the root during feeding
or invasion, are thus basically the same process.
 The pattern of this behaviour may vary according to the environment, and, although
the end results may be very different, the mechanism is the same

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