This document provides an overview of nemathelminthes, also known as roundworms. It discusses their classification into two classes: Aphasmidia and Phasmidia. Aphasmidia contains 6 orders including Enoploidea and Dorylaimoidea. Phasmidia contains 10 orders such as Rhabditoidea, Oxyuroidea, and Filarioidea. The document also outlines general characteristics of nemathelminthes such as their unsegmented, bilaterally symmetrical body structure; organ system level organization; and reproduction through sexual methods.

1. NEMATHELMINTHES
ASHOK KUMAR BOLLAPALLI
M.SC.,B.ED.,CSIR-NET,M.A(LIT) D.C.A.
LECTURER IN ZOOLOGY
KRK GOVT DEGREE COLLEGE
ADDANKI-523201
9652929696,9441635264
ASHOKKUMARZOOLOGY@GMAIL.COM

2. INTRODUCTION
• Gegenbaur (1859) included some pseudocoelomate
animals in a group called Nemathelminthes.
• NEMA= THREAD., HELMINTHES= WORMS
• Grobben(1910) called them as Aschelminthes( Gr., Askes=
Cavity, helmin= worm)
• Pseudocoel – a cavity between gut and body wall
(Pseudocoelomates)
• Bilaterally symmetrical and unsegmented worms

3. GENERAL CHARACTERS
1.Bilaterally symmetrical unsegmented worms
2.Triploblastic – Ecto,Meso,Endoderms
3.Organ system level of organisation
4.Body is cylindrical or flattened and is covered by a protective cuticle
5.Alimentary canal is straight tube with mouth and anus
6.Pharynx is muscular and specialised
7.Respiratory and circulatory systems are absent
8.Excretory system- canals, protonephridia- ormoregulation
9.Nervous system is simple with nerve ring and longitudinal nerves

4. GENERAL CHARACTERS CONTD..
10.Muscle fibres are circular and longitudinal.
11. Papillae , Bristles and eye spots form the sense organs
12. Sexes are separate
13. Reproduction is only by sexual method
14. Shell is present around the eggs
15. Cleavage of the egg is determinate and spiral
16. Larval form is absent
17.Mostly parasitic and some are terrestrial and aquatic.

5. CLASSIFICATION - NEMATHELMINTHES
Class Aphasmidia (Adenophorea) Phasmidia (Secernentea)
1 Caudal sense organs/ Phasmids
are present
Phasmids present
2 Amphids (internal sense organs)
of various types present
Amphids present and pore like
3 Caudal adhesive glands are
present
Caudal adhesive glands are absent
4 Excretory system is absent. If
present poorly developed
Excretory system is well
developed
5 Mesenterial tissue well developed Poorly developed
6 Divided into 6 orders Divided into 10 orders

6. Class – Aphasmidia(Adenophorea)
Sl.No Orders Examples
1 Enoploidea Enoplus
2 Dorylaimoidea Dorylaminus
3 Mermithoidea Mermis, Paramermis
4 Chromodoroidea Helichoanolaimus
5 Monohysteroidea Plectus, Monohystera
6 Desmoscolecoidea Desmoscolex

7. CLASS- PHASMIDIA (SECERNENTEA)
SL.NO ORDERS EXAMPLES
1 Trichiuroidea Trichiuris , Trichinella
2 Dictophymoidea Dictophyma
3 Rhabditoidea Rhabditis
4 Rhabdiasoidea Rhabdias, Strongyloides
5 Oxyuroidea Oxyuris , Enterobius
6 Ascoroidea Ascaris
7 Strongyloidea Strongylus, Anchylostoma
8 Spiruloidea Gnathostoma
9 Dracunculoidea Dracunculus
10 Filarioidea Wucheraria