1. Phylum Annelida – The Annelids (Segmented Worms)

2. Phylum Annelida Segmented Worms Leech Christmas tree worm Fireworm
Feather duster worm

3. Figure Annelids, the segmented worms: Polychaete (left), feather-duster worm (middle), leech (right)

4. Figure 33.24cx Christmas-tree worms

5. Annelids SEGMENTATION! Closed circulatory system Alimentary canal
Five pairs of hearts
Gas exchange across skin
Metanephridia for gas exchange
Nitrogenous wastes exit from each segment through pores
Nervous system with ganglia and ventral nerve cords

6. Figure 33.23 Anatomy of an earthworm

7. Three classes: Oligochaetes Earthworms Polychaetes: Fanworms
Tube dwellers (marine)
Hirudinea:
Leeches
Used to treat bruised tissues and to stimulate circulation

8. Table 33.4 Classes of Phylum Annelida

10. Annelid Systems
Complete digestive tract - some specialization - crop and gizzard
Closed circulatory system - is segmentally arranged dorsal and ventral vessels aortic arches (hearts)

11. The closed circulatory system is much more efficient!

12. Respiration
across body surfaces
some have gills
some use parapodia

13. Nervous system
ladder shaped
pair of cerebral ganglia
double ventral nerve cords
pair of ganglia in each segment
several sensory structures
taste buds
tactile organs
eyes in some
statocyst

14. Reproduction
some are monoecious, others dioecious
some have asexual reproduction by
Budding or Fragmentation

15. Class Polychaeta (“many bristles”)
Make up 2/3 of phylum
most primitive annelids; ancestral to other two classes
almost all are marine, few freshwater species
External sexual
fertilization

16. Class Oligochaeta “some bristles”
Spacious coelom
Live typically on land
Developed sensory organs but no eyes – clitellum used as copulatory
organ; cocoon forms here
Reproduce by hermaphroditic sexual reproduction

17. Figure 33.23x External anatomy of an earthworm
Class
Oligochaeta
Clitellum

18. Class Oligochaeta Digestive System - well differentiated mouth pharynx
crop
gizzard
intestine – Typhlosole increases surface area
anus

19. Class – Hirudinea Ex: leeches
Freshwater or terrestrial
Have suckers
Segmentation fixed
Clitellum only during season
Digestive tract
large crop
Anticoagulant in saliva
Medically important

20. Why we all  love worms…
They burrow in the ground allowing for air flow and water flow (keeps the ground aerated and moist)
Their waste fertilizes the soil we use
Many are detritivores; they eat dead material so we aren’t buried by it
They have been proven to promote plant growth
AND research has shown worms reduce the speed of erosion
Leeches have been used for centuries for medicinal purposes – even today they are used for their natural anti-coagulants to promote the growth of new capillaries so that tissue does not die after surgery