1. Annelids – Defining Characteristics
Segmented worms
Coelomates
Trochophore larvae
protostome

2. Segmentation

3. Annelids – Feeding
Filter feeders – use gills to capture food particles from water
Others use pharynx to either suck in food or to extend out and get it.
Some annelids have jaws on their pharnyx
Christmas tree worm 

4. Nereis – (clam worm) -has jaws for eating and fighting

5. Respiration Aquatic annelids use gills
Earthworm cuticle 
Aquatic annelids use gills
Terrestrial annelids exchange gases through their skin – their skin must remain moist for this purpose
Cuticle on the earthworm helps prevent desiccation
Feather-duster worm
– gills exposed (red)
- tentacles for gathering food

6. Internal Transport Closed circulatory system
Dorsal surface has blood moving toward the head, ventral surface moves blood away from the head
Each segment has a ring vessel connecting the ventral with the dorsal
Large ring vessels at anterior end act as a “heart” to pump the blood
If no heart is present, the bodies muscular contractions move the blood around

7. Excretion Solid wastes out the anus
Metabolic (liquid) wastes are eliminated by nephridia (like the nephrons in our kidneys)
2 nephridia/segment

8. Response Brain on dorsal surface
Nerves travel from the brain, around the gut and a main nerve cord travels down the ventral surface
Brain = #11
Ganglia = #12
Ventral Nerve cord = #13

9. Sense organs Best developed in free living annelids
Most of these have sensory tentacles, statocysts, chemoreceptors, and “eyes”
Some form images, some are light-detectors
Some have sensory organs that detect vibrations (like our tympanic membranes)
Spaghetti worm underground
With tentacles exposed

10. Self Defence Burrow into ground or swim away
Setae (bristles) anchor worms in the soil
Marine fan worms make tubes of CaCO3 to hide in
Tube worms 

11. Self-Defence Marine fireworms have poisonous bristles (burns)
Carnivorous annelids have jaws to bite their predators

12. Movement longitudinal muscles shorten the body
Circular muscles contract to decrease the diameter of the worm
Coordination of these sets of muscles allow the worms to wiggle, burrow and swim

13. Reproduction Some reproduce by budding
Some have separate sexes and have external fertilization
Palolo worms congregate at the surface and release sperm or eggs at the same time
Feast for the predators (humans included!)

15. Earthworms are hermaphrodites and exchange sperm
Sperm is stored in sacs until eggs are ready
Mucus ring is secreted by the clitellum – sperm and eggs are deposited there and the ring slips off the worm, forming a cocoon for the fertilized eggs

16. Common Characteristics in all Annelids
Unidirectional Digestive System
Closed Circulatory System
First sign of a ‘heart-like’ structure
Nephridia used for excretion
Primitive Brains present

17. Class Polychaeta – bristleworms
Mainly marine worm
Have padddle-like appendages with bristles
Show cephalization

18. More Polychaetes

19. Polychaetes

20. Class Oligochaeta - Earthworms and Relatives
Earthworms + Freshwater worms
Aquatic – eg tubifex (red, thread-like worms sold for fish food)
Oligo – means few (as in few bristles)
Castings are excellent fertilizer

21. Class Hirudinea Commonly known as the LEECHES
Fresh and saltwater species (~300)
Few land species
Muscular proboscis is forced into skin
Others slice skin with their jaws

22. Leeches
Hirudin – anti-coagulating chemical is used to keep host’s blood flowing
Some also use an aesthetic so the host does not know they are there
Used for medicinal purposes

23. Annelids aerate the soil by burrowing
Return nutrients to the soil completing decomposition of material
Many annelids are the basis of food chains

24. Internal Anatomy

25. Identifying practice: