Classification of Nematodes Nematodes are classified into the following classes: 1. Phasmidia or Secernentea • These are mostly parasitic. • Caudal glands are absent. • Unicellular, pouch-like sense organs called plasmids are present. • The excretory system has paired lateral canals. • Eg., Ascaris, Enterobius 2. Aphasmidia or Adenophorea • They are free-living organisms. • The excretory system has no lateral canals. • Caudal glands are present. • Phasmids are absent. • Eg., Capillaria, Trichinella

1. GENERAL CHARACTERISTICS
Nemathelminthes

2. Phylum Aschelminthes/
Nemathelminthes
Askos: cavity; helmins: worms.
Nema: thread, helmins: worms

3. 1. They are commonly called thread
worm or round worm.
2. It is a phylum of unsegmented,
triploblastic, pseudocoelomic,
cylindrical or thread-like worms
3. Which are covered by a body
wall having cuticle and epidermis.

4. 4. Mostly parasitic. Few of them are
free-living.
5. They are cylindrical, elongated,
slender worm like and tapers at both
end.
6. Triploblastic.
7. Bilaterally symmetrical.
8. Organ system level of organization.

5. 9. Body is unsegmented.
10. Body cavity is filled with muscle.
11. They are pseudocoelomate i.e.
body cavity is not lined by
mesodermal layer.
12. Internal cephalization is present
but externally there is little
differentiation between the anterior
and posterior regions

6. 13. Distinct head is lacking. However,
mouth is present in anterior region.
14. Body is covered with tough and
resistant cuticle.
15. It is cast off periodically or which
moults only during the period of
growth.

7. 16. It protects the body against
the action of digestive juice.
17. Digestive system is complete
and straight with both mouth and
anus.
18. Mouth is terminal and
surrounded by lips bearing sense
organ.

8. 19. Respiratory and circulatory
organs are absent.
20. Respiration occurs through
general body surface. Respiration is
aerobic in free-living forms and
anaerobic in parasitic form.
21.Excretory system consists of
intracellular canal or lateral
excretory ducts. And also
protnephridia having renette cells.

9. 22. Nervous system is not much
developed.
23. Nervous system consists of
circumpharyngeal nerve ring and
longitudinal nerve cords.
24. Sense organs are poorly developed
in the form of papillae, which are well
defined as amphids (in mouth) and
phasmid (in anus).

10. 25. These are unisexual i.e. sexes are
separate with sexual dimorphism.
26. Fertilization is internal, may be cross
or self.
27. Development may be direct or
indirect.
NOTE: Larval forms are Rhabditiform,
Filariform and Micrifilaria.
Various lateral lines and pores are
present on the surface of body.

11. Classification

12. Aphasmida (Adenophora) Phasmida (Secernetea)
Caudal sensory organs (Phasmid)
are absent.
Phasmids are present.
Anterior sensory organs (Amphids)
are of various types.
Amphids are pore like.
Usually free living. Usually parasitic.
Excretory system absent or
rudimentary.
Excretory system well developed
with renette cells.
Tail is non-glandular. Tail is glandular.
Examples: Trichinella, Dorylaimus
Examples: Ascaris lumbricoides,
Enterobius vermicularis
Phylum Nematod is classified into two
classes on the basis of sensory organ

13. I. Class Adenophorea
(Aphasmida):
i. The members possess variously
shaped amphids behind the lips.
ii. Absence of phasmid in the
caudal area.
iii. Presence of cephalic setae and
papillae.

14. iv. Presence of paired testes.
v. Most of the species in this class are
free- living (terrestrial and fresh
water forms), some are parasitic.
This class comprises of twelve orders.
Examples:
Mondnchus, Dorylaimus, Trichinella,
Trichuris.

16. The class Adenophorea or
Aphasmida contains the following orders:
Order 1. Enoplida: Ex. Enoplus,
Anticoma, Metonchdiamus.
Order 2. Dorylaimida: Ex. Dorylaimus,
Tylencholaimus, Xiphinema, Trichodoris.
Order 3. Mermithida: Ex: Mermis,
Agamermis, Paramermis.

17. Order 4. Chromadorida: Ex:
Paracanthonchus, Paracytholaimus.
Order 5. Desmoscolecida: Ex:
Desmoscolex, Greefiella, Epsilonema.
Order 6. Monohysterida: Ex:
Monohystera, Saiphonolaimus.
Order 7. Araeolaimida: Ex: Plectus,
Odontophora, Wilsonema.

18. II. Class Secernentea (Phasmida):
i. This class comprises of nematodes
that usually possess pore-like
amphids in the lateral lips.
ii. In the caudal region there is the
presence of a pair of phasmid.
iii. Only anterior testis is present.

19. iv. Many parasitic forms are
member of this class and the
free-living species largely
inhabit soil.
Examples:
Ascaris, Wuchereria,
Ancylostoma, Rhabditis, Loa
loa (eye-worm)

21. This class comprises of eight orders.
It includes certain important orders:
Order 1. Rhabditida: Ex. Rhabditis,
Heterodera, Bunonema.
Order 2. Strongylida: Ex:
Ancylostoma duodenale (Hookworm),
Strongylus, Trichostrongylus (Hair
worm), Ne-cator.
Order 3. Oxyurida: Ex: Oxyuris,
Enterobius vermicularis (Pinworm),
Thelastoma, Aspiculuris.

22. Order 4. Ascaridida: Ex: Ascaris
(Ascaris lumbricoides, Ascaris
megalocephala, Ascaris suillas),
Parascari, Toxocara.
Order 5. Spirurida: Ex: Spirura,
Wuchereria bancrofti (Filaria), Loa
loa (Eye worm), Brugia, Onchocerca,
etc.

23. Order 6. Trichuroida Ex: Trichuris
(Parasites of mammals), Trichinella
spiralis (Trichinia worm).
Order 7. Dracanculayida: Ex:
Camallanus, Procamallanus,
Dracunculus medinensis (Guinea-
worm), Philometra.

24. 8. Rhabtiyusayidia: Rhabdius
9. Failariyayida: Uchareris
10. Oxyuraidia: Entirobius