1. The document discusses the morphology, general characteristics, and biology of plant pathogenic nematodes. 2. It describes the typical structures of nematodes including the stylet, median bulb, isthmus, nerve ring, and reproductive organs. 3. The life cycle of plant parasitic nematodes involves eggs hatching into juveniles that molt four times before becoming sexually mature adults.

1. Dr. Amol. J. Deshmukh
Assistant Professor
amol_deshmukhnau@nau.in
College of Agriculture
Navsari Agricultural University,
Waghai (Dangs) – 394730.
2
Morphology, General characteristics
and biology of plant pathogenic
nematodes

2. https://youtu.be/qCy-eDPq4Ws
Complete explanation of this presentation was
also available on you tube
link………………………………

3. Typical plant parasitic female and male
nematodes

5. Stylet: Piercing apparatus of plant parasitic nematode usually consists of a
slender, hollow tube with an anterior cone and posterior shaft or knobs
Stylet knob: Swellings at the base of nematode stylet is called as stylet knob
Procorpus: The anterior subdivision/ portion usually cylindrical part of the
nematode corpus is called as procorpus
Metacorpus/ median bulb: The posterior subdivision/ portion usually circular
or oval part of the nematode corpus preceded by procorous is called as
metacorpus or median bulb
Isthmus: The segment between the median bulb and basal bulb of the pharynx
where the nerve ring is located is called as Isthmus
Nerve ring: Circumesophageal or circumpharyngeal arrangement
of nerve ganglia around the esophagus/ pharynx of a nematode is called as
nerve ring
Excretory pore: The ventral opening of the excretory system through which
excretory / waste products are emitted out from the nematode body
Oesophagus/ pharynx: The part of the alimentary canal which connects the
throat/ stoma to the stomach/ intestine
Cardia: The upper opening of the stomach, where the oesophagus enters is
called as Cardia

6. Intestine : A simple tube composed of a single layer of epithelial cells in which
digestion of food takes place
Testis: an organ which produces spermatozoa (male reproductive cells).
Spicule: Sclerotized, needle-like mating structures of male nematodes which serve to
open the vulva of females, and facilitate the transmission of sperm.
Cloaca: In the male a common chamber lined with cuticle which receives the
products of the intestinal and reproductive tracts and empties to the exterior via the
anus.
Bursa/ caudal alae: Wing like extensions of the lateral cuticle of the male
Spermatheca: The enlarged portion of the female reproductive system which
functions as a reservoir in receiving and holding sperms from the male
Uterus: A region of the oviduct modified to function as a place of development
(sometimes for maturation) of the egg.
Vagina: A canal lined with cuticle connecting the uterus or the ovijector with the
vulva
Vulva: The transverse slit of the female genital opening situated on the ventral line
in most of the genera
Vas deferens: The duct which conveys sperm from the testicle to the urethra
Anus: The extremity of the rectum. The posterior opening of the alimentary canal is
called as Anus

7. Female

8. Male

12. Triploblastic: organisms having a body derived from
three embryonic cell layers (ectoderm, mesoderm, and
endoderm)
Blastula : An animal embryo at the early stage of
development when it is a hollow ball of cells.
Gastrulation : The process by which a gastrula forms
from a blastula. "during gastrulation, cells move into
the interior of the embryo"

13. GENERAL CHARACTERS OF NEMATODE
1. The nematodes possess elongate, unsegmented, cylindrical or
worm like body tapering towards both ends, unciliated and
circular in cross section.
2. Body is bilaterally symmetrical.
3. These are triploblastic in nature
4. They are aquatic, terrestrial and parasitic or free living.
5. The body is covered by tough and resistant cuticle secreted by
epidermal (hypodermal) cells.
6. Terminal oral aperture (mouth) surrounded with lips and
papillae.
7. Digestive system consist of feeding apparatus, oesophagus,
intestine and rectum.
8. Body consist of two tubes.
9. The nervous system consist of circum-oesophageal nerve ring
and longitudinal nerves.
10.Primitive excretory system, is devoid of protonephridial cilia or
matanephridial funnel.
11.The circulatory and respiratory systems completely absent.
12.The females have separate genital pore and males have a
common opening known cloaca and well developed copulatory
apparatus consisting of spicules and gubernaculum.
13.Females are oviparous or ovoviviparous or viviparous. The
cleavage is terminate and growth is accompanied by molting.
14.Life cycle is direct and there are four juvenile stages.

14. The outer body tube
1. The outer body tube or body wall includes the cuticle, hypodermis,
and somatic muscles.
2. The body wall protects the nematode from the harsh external
environment, serves as the exoskeleton and provides the mechanism
for movement of the organism through the soil and plant tissue.
3. The body wall also contains much of the nervous and secretory-
excretory systems, and it plays a role in the exchange of gases.
The cuticle or exoskeleton
1. The cuticle is a non living, non cellular, triple - layered covering
secreted by the underlying hypodermis.
2. The cuticle is flexible.
3. It covers the entire body and lines the esophagus, vulva , anus ,
cloaca, excretory pore and sensory organs.
4. The stylet and copulatory spicules are formed from cuticle.
5. The cuticle of nematodes have markings on the surface. They are
varied and complex and have been often used by taxonomists to assist
in the identification of various species.
6. The cuticular markings are categorized into different types. 1.
Punctuation 2. Transverse or striations and 3. longitudinal
markings. through which cuticular proteins may be transported
The function of cuticle:
Cuticle gives definite shape and size to the body, acts as an exoskeleton,
helps in movement, being semi permeable, it regulates permeability and
provides important taxonomic characters for identification of nematodes.

17. Inner Body Tube/Digestive system
It is divided into 3 main regions.
1. Stomodeum: stoma/ buccal cavity, oesophagus / pharynx
2. Mesenteron: intestine/ midgut
3. Proctodeum: rectum and anal opening/ hindgut
1. Stomodeum:
Stoma: It is the portion lying between oral opening and
oesophagus. The stomatal opening is small and slit like and is
surrounded by six lips. Two sub dorsal, two sub ventral and two
lateral. Plant parasitic nematodes are armed with a protusible
stylet which is usually hallow and functions like a hypodermic
needle. Stylet with basal knob are called as Stomatostylet
e.g.Tylenchida and the stylet without basal knob are called as
odontostylet or onchiostylet e.g. Dorylaimida.
Oesophagus or pharynx: Oesophagus is a muscular organ
attached to the posterior portion of the stylet and lines with
cuticle. The oesophagus is divided into a narrow anterior
procorpus, broad posterior corpus followed by a broad muscular
median bulb or pump, a narrow isthmus and gland lobe. The
oesophagus has valve (cordial) at the posterior end which
prevents the regurgitation of food.

19. 2. Mesenteron or intestine or midgut
The nematode intestine is a simple, hallow, straight tube
consisting of a single layer of epithelial cells. The intestine is
generally divided anterior or ventricular region, the
midintestinal region and the posterior or prerectal region which
merge in to each other without any perceptible boundaries and
increase the surface area of the intestine and are both secretary
and absorptive in function. The whole intestine is separated
from the pseducoelom by a basement membrane. The food
moves in the intestine by the ingestion of more food and also by
locomotory activity of the nematode.

20. 3. Proctodeum
Proctodeum comprises rectum and anus. The intestinal tube
is connected with a narrow small tube at the posterior end
through a valve known as rectum. It regulates the flow of
undigested food material which is to be passed outside the
nematode body through a ventrally located aperture known
as anus. In male nematode, the rectum joins with the hind
part of the testis forming a common opening known as
cloaca. In female, there is a separate opening.

21. Glands
Oesophageal and rectal glands are present in nematodes. The
oesophageal gland enters the stomodeum and rectal gland enter
proctodeum.
Oesophageal glands
Three uninucleated oesophageal glands. One gland on dorsal and
other two ventro lateral or sub ventral in position. The gland connect
with the lumen of the oesophagus .The oesophageal glands have
important role in hatching host penetration and also establishment of
host parasitic relationship.
Rectal glands
Responsible for the copious production of gelatinous
mucopolysaccharide matrix in which eggs are deposited as a mass. It
protects the eggs from adverse environmental conditions.
Function of digestive system
Digestive juices secreted from dorsal oesophageal glands are injected
into the host plant cell by means of the stylet. During feeding a
distinct zone develop around the feeding site in the host cell.
There are two feeding phases.
1. Injection phase or Salivation phase: During this phase, the flow of
salivary juices into the host cell occurs due to contraction of lateral
muscle of the median bulb.
2. Ingestion phase: During this phase rhythmical contraction of the
posterior part of the oesophagus associated with the medium bulb
occurs.

24. Biology of Plant Parasitic Nematodes
Under biology, the life cycle of nematode is studied. The
life cycle of plant parasitic nematodes is simple and direct.
In all six stages or instars are found in the life cycle of a
primitive nematode:
1. The egg
2. The first stage larva or juvenile (J1)
3. The second stage larva or juvenile (J2)
4. The third stage larva or juvenile (J3)
5. The fourth stage larva or juvenile (J4)
6. The adult
The first four stages are the immature stages and are known
as juvenile stages. The female lays eggs in soil or in plant
tissues, singly or in groups as egg mass that hatch out into
larvae which are almost similar to adults in appearance. The
first moult occurs within the egg shell and the second stage
juvenile comes out by rupturing the egg shell as J2, Further
moulting leads to J3, J4 and adult.

25. Life Cycle of Root-Knot Nematodes
 Sedentary endoparasitic in nature
 Males vermiform , non parasitic
 Females embedded inside galls
 Lays 200-400 eggs in mass in gelatinous matrix.
Egg are oval in shape
 Pre embryonic (in egg) &post embryonic
development (J2 to egg laying)
 J1-M1-J2-M2-J3-M3-J4-M4-Adult
 Hatching in water-no stimuli required
 J2 infective stage
 Pre-parasitic J2 attract towards roots due to root
exudates
 J2 penetrates roots behind root tip

26.  Moves in roots & take position near vascular tissues
 Become sessile
 Giant cells formed due to hypertrophy and hyperplasia
occurs
 Become swollen , known as parasitic J3
 Sex differentiation occurs in J3
 Females acquires V-shape genital primordium while in
male I shape
 J3 &J4 are not feeding because they have no stylet
 After M4, adult female become sac- like, stylet reappear,
reproductive system fully developed
 J4 males are vermiform, come out from roots
 Life cycle completed in about 25 days at 25-300C
 In winter life cycle prolonged to 60-68 days
 7-8 generations are completed in a year

28. (1) Entry of second-stage juveniles into root tip (2) intracellular
migration of J2 in cortex (3) establishment of feeding site in vascular
system (4) molt to third-stage juvenile (5) molt to fourth-stage juvenile
(6) development of young females (7) egg formation in healthy female
(8,9) healthy female releases egg masses

29. https://youtu.be/qCy-eDPq4Ws
If you like the presentation you
can access above link for detailed
explanation ….
Complete explanation of this presentation was also available
on you tube link………………………………

30. Thank you