1. Phylum: Annelida - segmented worms
Class: Oligochaeta
Class: Polychaeta
Class: Hirudinea

2. Oligochaeta

3. Class: Polychaeta Bristle worm
is poisonous and attacks sea anemones

4. Class: Hirudinea

5. Christmas tree worm

6. Class: Polycheata

7. P O L Y C H A E T
C L A S S

8. Yikes!!

9. Characteristics of Phylum :Annelida—Little rings
True coelom
Each compartment is surrounded by peritoneum which forms dorsal and ventral mesenteries that covers all the organs
Hydrostatic skeleton
Closed circulatory system

10. True coelom

11. *Centralized Nervous System*
Brain
Double ventral nerve cord
Pair of ganglia in each segment
Lateral nerves

12. *Centralized Nervous System*

13. Sensory organs Taste buds Statocysts - balance sensory receptor
Photoreceptor eyes with lenses in some

14. Circulatory System Blood flows entirely in closed vessels
Some spp. have hearts
Blood contains hemoglobin, which increases oxygen carrying ability
Phylum Annelida

15. Excretory system
Pair of nephridia in each segment

16. Respiration By gas exchange through Skin Gills
Parapodia - fleshy paired appendages

17. Body plan Bilateral Metameric-repeating segments
(metamerism allows for budding)
Setae-small hairs or sometimes parapodia, i.e. small appendages

18. Body plan Setae (“bristles”) of chitin “anchors” for earthworm
“paddles” for polychaete
Enlarged as jaws in leeches, some polychaetes

20. Reproduction
Sexes are usually separate with gonads occurring in each segment
Some species have gonad specific segments
Breeding is usually seasonal (spring or fall)
As gametes mature they fill the coelom and are released by the nephridia
Fertilization can be internal or external
Trochophore larvae develop, which are remarkably similar to the Molluscs

22. Skin
Contains glands to secrete mucous and setae

23. Nutrition Eat any dead organic material
Consume up to one half their body weight every day

24. Nutrition
Annelids range from carnivores, herbivores, scavengers, deposit feeders, and filter feeders
With very few defenses, many remain in a burrow or secreted tube
Carnivores can capture prey with strong jaws and quickly drag it back to its burrow
Can use a muscular pharynx = eversible proboscis

25. Digestion mouth esophagus crop intestines gizzard
Mechanical –grinding in the gizzard
Chemical in the intestines
Extracellular and intracellular digestion

26. Environmental role Can be found in fresh water, salt water, soil
Helps aerate/renutrify gardens
Medicinal purposes

27. Classes
How do we classify these segmented worms into different classes?

28. Class: Polychaeta (many setae or hairs)
20+ setae per segment
Well differentiated head
Specialized sense organs
Parapodia
No clitellum
Mostly marine predators, e.g. “Barry” the seaworm

29. Class: Polychaeta (many setae or hairs)

30. Class: Oligochaeta (Few long hairs)
Clitellum
Few long, short or straight setae; 2-4 clusters per segment
Land or marine, some parasites

31. Class: Oligochaeta (Few long hairs)

32. Class: Hirudinea Flattened dorsalventrally
Mostly freshwater, some marine
Fluid feeder (blood)
Clitellum
Setae have developed suckers
Specialized proboscis

33. Class: Hirudinea Class Hirudinea pair of bladelike “jaws”
posterior “suction cup”
Predators
External parasites, “bloodsuckers”
Secrete anticoagulants
Medicinal use

34. Blood Sucker
The salivary glands excrete hirudin which prevents the blood from coagulating
May also secrete an anaesthetic and substance to dilate small blood vessels
Blood is broken down by symbiotic bacteria that is then used by the leeches
Leeches were commonly used in the 19th century for bloodletting
Recent medical uses are to relieve pressure after vascular tissue is damaged
Snake bites or the reattachment of a finger or ear
Phylum Annelida