1. Annelida
Segmented Worms

2. Characteristics of Phylum Annelida
Metameric body(segmented), Bilateral symmetry
Trochophore larvae, Spiral cleavage
Paired epidermal setae (chaetae)
Closed circulatory system
Dorsal suprapharyngeal ganglia and ventral nerve cord with ganglia
Metanephridia or protonephridia

3. Phylum Annelida, 2 Classes
Class Polychaeta- mostly marine, head with eyes and tentacles, Parapodia with numerous setae
Class Clitellata- no parapodia, few or no setae, clitellum functions in cocoon formation
Subclass Oligochaeta- few setae, no distinct head, terrestrial and freshwater, earthworms
Subclass Hirudinea- bodies with 34 segments, posterior and anterior suckers, freshwater, marine and terrestrial, Leeches

4. Metamerism and Tagmatization
Segmental arrangement of body parts internally, functions in flexible support and efficient locomotion
Compartmentalization has resulted in each body part having its own excretory, nervous and circulatory structures
Coelomic spaces allows hydrostatic compartments controlled independently
Lessens impact of injury, separates injured segments

5. Metamerism and Tagmatization
Tagmatization- modification of regions of body for specialized functions, ex. feeding, locomotion, reproduction
Each segment contains layers of circular muscles, longitudinal muscles and some polychaetes have oblique muscles and leeches have dorsoventral muscles
Each segment can be controlled independently, muscles act as antagonistic pairs
Coelomic fluid provides hydrostatic skeleton against which muscles operate

6. Excretion Annelids excrete ammonia mostly thru body wall
Excretory organs (nephridia) discharge waste and regulate water and ion balance
Protonephridia- tubule with a closed bulb at one end and the other opening outside the body, Bulb contains flagella that drives fluid thru tubule
Metanephridia- open ciliated funnel at one end of coiled tubule open to outside of body or intestine at other, coil may be dilated into a bladder and connected to capillaries

7. Class Polychaete
Polychaete (many hairs) mostly marine, 5 to 10 cm long
Live on ocean floor, under rocks, crevices of coral reefs, burrow in mud and sand, some construct tubes of cemented sand grains or secreted organic material
Parapodia- lateral extensions of segments with setae (bristles) projecting out, internal support of chitinous rods
Various species are capable of walking, fast crawling, or swimming

8. Polychaete

9. Polychaete with Parapodia

10. Chloeia Polychaete

12. Polychaete Head

13. Parapodia

14. Bristle Worm Needles

15. Polychaetes
Prostomium- anterior lobe contains eyes, antennae, palps and ciliated grooves (nuchal organs)
Peristomium- first body segment, surrounds mouth and sensory tentacles
Epidermis contains single layer of cells, secrete protective cuticle, some secrete luminescent compounds

16. Polychaete Feeding
Proboscis- anterior digestive tract can be everted thru the mouth
When proboscis is everted paired jaws seize prey, some have poison glands at base of jaws
Others are herbivores and scavengers, use jaws to tear food
Digestive tract consists of pharnyx (proboscis), crop, gizzard and long straight intestine

17. Filter Feeders
Usually lack a probocis but have other feeding structure
Fan worms- tube dwellers with funnel shaped fan (Radiole), cilia on radiole circulate water and trap food, push food towards mouth
Chaetopterus lives in U shaped burrow, secretes mucos bag to collect food. Modified parapodia on segments create current

18. Fan Worms

19. Fan Worms

20. Feather Duster worm

21. Plume Worm

22. Christmas Tree Worm

23. Christmas Tree worms

24. Christmas Tree Worms

25. Chaetopterus

26. Chaetopterus

27. Sensory Structures
Pair of suprapharyngeal ganglia leading to subpharangyal ganglia connected to a double ventral nerve cord, ganglia at each segment with lateral nerves
Suprapharangyal ganglia- motor and sensory functions
Subpharangeal ganglia-coordinate locomoter functions of segments
Eyes 2 to 4 pairs, nuchal organs(chemoreceptors), statocysts, palps for tactile sense

28. Class Clitellata
Subclass Oligochaeta- Earthworms and relatives, few or no setae
Terrestrial, freshwater and a few marine species
Known for their soil conditioning habits
Body smoothed for burrowing in soil
Swollen segments near anterior form clitellum which secretes cocoon for eggs

29. Earthworm Anatomy
Locomotion involves antagonism of circular and longitudinal muscles, segments bulge setae stiffen when longitudinal muscles contract, circular muscles make segments elongate and push forward
Burrowing by swallowing and compacting soil
Feed on decaying vegetation
Mouth, esophagus crop, gizzard, intestine with dorsal fold to increase surface area

30. Earthworm Anatomy

31. Earthworm Anatomy
5 Aortic arches (hearts) push blood down dorsal blood vessel and returns by ventral vessel, blood vessels serve propulsive structures also
No well developed eyes due to subterranium lifestyle but do have photorecptor cells in skin
Dorsal blood vessel contains chloragogen tissue, acts like a liver converts ammonia to urea, converts carbohydrates into fat and glycogen

32. Earthworm Cross section

33. Earthworm Reproduction
Monecious contain two pairs of testes and one pair of ovaries, exchange sperm
Clitellum forms cocoon made of mucous and chitin material, food reserve (Albumen) and sperm and eggs secreted into cocoon and worm backs out, fertilization occurs in cocoon

34. Trochophore

35. Leeches Subclass Hirudinea
Freshwater (most), marine and terrestrial
Prey on small invertebrates or body fluids of vertebrates, specific hosts- fish, alligator and turtle, mammals
Flattened dorsoventrally and taper anteriorly Have 34 segments, anterior and posterior segments modified into suckers
Single coelomic body cavity, loss of internal compartments, circular, longitudinal and transverse muscles

37. Engorged Leech

38. Leeches Mouth modified into extensible proboscis, or has 3 jaws
Attaches with anterior sucker, bores into host
salivary glands secrete anticoagulant (hirudin)
Muscular pharnyx pumps body fluids of prey, leech gorge themselves, increase 2 to 10 times
Attracted to temperature (mammals) or extracts of prey tissue

39. Marine Worms
Echiurans (spoon worms) burrow in sand, extend spoon shaped proboscis up to 2 meters long to sweep food
Siboglinids (beard worms) tube dwelling worms embedded in marine sediments, no mouth or digestive tract, nutrients enter thru skin or derived from endosymbiotic bacteria, giants live near thermal vents
Sipunculans ( peanut worms) live in mud and sand, tentacles surround mouth for feeding

40. Echiurans (spoon Worm)

41. Echiurans (spoon worms)

42. Siboglinids (beard worms)

43. Sipunculans (peanut worms)