Nemathelminthes general characters and classification

HISTORY
GENERAL CHARACTERS
CLASSIFICATION

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 [email protected]

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 Bilaterally symmetrical unsegmented worms Triploblastic – Ecto,Meso,Endoderms Organ system level of organisation Body is cylindrical or flattened and is covered by a protective cuticle Alimentary canal is straight tube with mouth and anus Pharynx is muscular and specialised Respiratory and circulatory systems are absent Excretory system- canals, protonephridia - ormoregulation 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