View
230
Download
0
Category
Preview:
Citation preview
Topics
Size
Shape
Body wall (Outer body tube)
Digestive system (inner body tube)
Reproductive system
Excretory system
Nervous system
Respiratory and Circulatory systems
Definition
2
7/20/2017Walia CCSHAU
Size
Human and Animal parasites are big and visible to the naked eyes Ascaris lumbricoides …………………...30 cm
Dracunculus medinensis……………….1m
Placentonema gigantissimma ………...8 m (longest)
Free-living nematodes microscopic Greeffiella minutum…………………….82 µm (smallest)
Plant parasitic nematodes Microscopic, range……………………..0.3 – 2.0 mm
Paralongidorus epimikis ……………1.2 cm (longest)
3
7/20/2017Walia CCSHAU
Body regions, Colouration, Segmentation
Head – Continuous or set off
Tail - body portion beyond anus, shapes variable
Appendageless
Colourless
Body wall transparent
No metameric segmentation
All natural openings on one side - ventral side
6
7/20/2017Walia CCSHAU
Body Organization and Symmetry
Body tubular Outer tube – Body wall
Inner tube – Alimentary canal
Body Cavity – Pseudocoelome
Bilateral symmetry
7
7/20/2017Walia CCSHAU
Cuticle
– Non-cellular
– Tough but elastic
– Exoskeleton
– Regulates permeability
– Regulates body growth
– Helps in locomotion
– Plays role in respiration
– Plays role in excretion
– Moults four times
– Consists of structural proteins
(keratin, collagen, matricin)
– Chitin absent in cuticle
9
7/20/2017Walia CCSHAU
Cuticular markings
A.Transverse
Smooth Striated Annulated
Striated Annulated
10
7/20/2017Walia CCSHAU
Cuticular markings
Caudal alae (Bursa)
Leptoderan Peloderan
B. Longitudinal
Lateral alae
11
7/20/2017Walia CCSHAU
Hypodermis & Musculature
Hypodermis: Cellular or syncytial, secretes new cuticle after every moult,
forms 4 hypodermal chords
Musculature : Somatic, Specialized
12
7/20/2017Walia CCSHAU
Musculature
Somatic muscles Attached to body wall
Nvbnvbn
• Specialized musclesAssociated with special organs e.g., stylet, spicules
A. Platymyarian B. Coelomyarian C. Circomyarian
13
7/20/2017Walia CCSHAU
Alimentary Canal – The Inner Body Tube
Stomodaeum – The Fore gut
Oral aperture (Mouth)
Stoma ( Buccal cavity)
Oesophagus (Pharynx)
Cardia (Oesophago-intestinal valve)
Mesenteron – The Mid gut
Intestine
Proctodaeum – The Hind gut
Rectum
Anus
14
7/20/2017Walia CCSHAU
Stomodaeum - The StyletStomatostylets in Tylenchids
Conus
Shaft
Knobs (
3)
Lum
en
18
7/20/2017Walia CCSHAU
The Mesenteron and Proctodaeum
MesenteronIntestineWall made up of single layer
of epithelial cells;
inner margins lined with microvilli
ProctodaeumRectumIn males, intestine joins vas deferens
to form common tube – cloaca
AnusFemales have a separate opening;
pore-like on ventral side
22
7/20/2017Walia CCSHAU
Reproductive System
Nematodes are dioecious
Both sexes look alike
Reproductive system is tubular
Males v/s Females
• Males are slightly shorter
• Tail end curved ventrally
• Possess secondary sexual organs
• Spicules
• Gubernaculum
• Bursa
23
7/20/2017Walia CCSHAU
Female Reproductive System
Ovary
Germinal zone: Production of oogonia
Growth zone: Oogonia increase in size
Oviduct
A narrow passage for oogonia
Spermatheca
Store sperms; oogonia get fertilized
when pass through
Uterus
Columellar glandular cells – deposit
egg shell around fertilized egg
Vagina
Expulsion of egg
Vulva
Slit-like on ventral side; help in egg
laying and copulation
24
7/20/2017Walia CCSHAU
Female Reproductive System
Terminology
No. of genital tracts• Monodelphic
One
• Didelphic
Two
Direction of genital tracts• Prodelphic
Directed anteriorly
• Opisthodelphic
Directed posteriorly
• Amphidelphic
One directed anteriorly,
second posteriorly
25
7/20/2017Walia CCSHAU
Male Reproductive System
TestisProduction of spermatogonia
Seminal vesicleStorage of sperms till mating
Vas DeferensPassage for sperms, merges with intestineto form cloaca
CloacaCommon tube for digestive and reproductive systems
Cloacal apertureCommon opening for both systems
SpiculesSclerotized, a pair, movable, mating organ
GubernaculumPlate-like, not movable, guides the movement of spicules
BursaExternal cuticular extensions on lateral side, a pair, leptoderan or peloderan, hold female during mating
26
7/20/2017Walia CCSHAU
Excretory System
Phylum Nematoda divided into two classes based on the type of excretory system
Function speculatory, may be secretory, osmotic regulation etc.
Canalicular or Tubular typePresent in Class Secernentea
Basically H–shaped, variable
Two main longitudinal excretory ducts running
in lateral hypodermal chords
Joined in oesophageal region by a transverse duct
A terminal duct arises and opens on ventral side -
the excretory pore
Glandular typePresent in Class Adenophorea
Single (Renette) cell leads to an excretory duct
and opens outside through pore
27
7/20/2017Walia CCSHAU
Nervous System
• Main nerve centre (Brain)
is a ring called Nerve Ring
or Circum-oesophageal commissure
encircling the isthmus region of
oesophagus
• Main nerves arise from nerve ring
and run anteriorly and posteriorly
in the hypodermal chords
• These longitudinal nerves are
interconnected at regular intervals
throughout length
28
7/20/2017Walia CCSHAU
Sense organs
• Chemoreceptors(to perceive the sense of chemicals in vicinity)
AmphidsA pair, opening on lateral sides in head region,
help in locating plant roots
(Host finding/Chemotaxis)
PhasmidsA pair, opening on lateral sides in tail region,
enlarged phasmids are called Scutellae
• Tactoreceptors(to perceive the sense of touch)
Papillae/SetaeCephalic
Cervical
Caudal
29
7/20/2017Walia CCSHAU
Other Systems
Respiratory System
Well developed organs lacking
Oxygen required for aerobic PPNs diffuses through cuticle
Circulatory System
Well developed organs lacking
Pseudocoelomic fluid serves as the means of transport since it bathes different organs
30
7/20/2017Walia CCSHAU
Definition
Nematodes are triploblastic,
bilaterally symmetrical,
unsegmented,
pseudoceolomate invertebrates,
with four main hypodermal chords,
a triradiate oesophagus,
circum-oesophageal nerve ring,
and lacking specialized organs for
respiration and circulation;
they have tubular gonads
which open separately in females
but join alimentary canal in males
to open through a cloacal aperture.
Gross Morphology
31
7/20/2017Walia CCSHAU
Recommended