2. Class Clitellata
• Include earthworms and leaches.
Symplesiomorphic Characters:
1. Clitellum for cocoon formation.
2. Few or no setae.
3. Monoecious

3. Subclass Oligochaeta
• 3,000 species
• Aquatic as well
as terrestrial.
• Include earthworms.

4. External Structure
• Few Setae.
• Prostomium having small lobe.
• Clitellum.
• Cuticle.

5. .

6. Locomotion
• Antagonism of circular and longitudinal
muscles.
• Burrowing ……..Coelomic hydrostatic
pressure.

8. Feeding and digestive system
• Scavenger .
• Depend on fallen and decaying vegetation.
Digestive system:
• Tubular and straight.
• Mouth Pharynx crop gizzard calciferous
gland Anus
• Typhlosole.

9. Gaseous exchange and Circulation
• Respire through body wall.
CIRCULATION
• The blood system is a closed system.
• Blood…..head to the tail in the ventral vessel
tail to the head….. in the dorsal vessel
• Photoreceptors are present

10. Nervous system
–Dorsal brain
–Pair of nerves on sides of esophagus
–Paired ventral nerve cords with paired
ganglia in each segment
–Transverse nerves connect ganglia in
each segment

12. Excretion: Metanephridia

13. Reproduction:
• Monoecious.
Sexual reproduction
• Through copulation….. cocoon formation.
Asexual reproduction
• Transverse division
• Regeneration of parts