The document discusses the characteristics and classification of phylum Annelida, which includes metamerically segmented and coelomate animals such as polychaetes, oligochaetes, and hirudineans. Key features include distinct body structures like setae, sensory organs, and excretory systems, as well as specific examples like nereis and earthworms. It also highlights the leech's parasitic nature and its unique enzyme, hirudin, used for feeding.

1. PHYLUM ANNELIDA
(Metamerically segmented and coelomate animals)
Prof. S D Rathod

2. Annelids
 Soft bodied, triploblastic,
bilaterally symmetrical
and true coelomates
 Divided into the
segments called as annuli
 Excretion is performed by
nephridia

3.  Nervous system well developed and has brain

4. Class – Polychaeta: (animals
with many setae)
 Setae are many form
lateral parapodia
 Head is distinct with
sensory organs like
eyes, tentacles, palps
etc
 Free swimming larval
stage is found called
as trochophore
 example - Nereis

5. Parapodia
 Heteronereis

6. Tube dwelling polychaetes
 Arenicola Sabella

7. Class – Oligochaeta: (
animals with few setae)
 Setae few and are
arranged segmentally
 Distinct head eyes and
tentacles are absent
 Clitellum is usually
present
 example - Pheretima
(earthworm)

8. Class – Hirudinea: (Class of leeches)
 Ectoparasitic and
fresh water forms
 Secrete an enzyme in
its gut called as
hirudin
 33 segments
 Oral sucker. Posterior
sucker
 Anus is present in 22nd
segment on dorsal
side.

9. Leech bite

10. Good bye!!!!!!