1. Phylum Annelida Annelus = “ Little Ring” The Segmented Worms

2. Review Discuss 3 things you learned about unsegmented worms
(Recall unsegmented worms are:
Phylum Platyhelminthes (flatworms)
Phylum Nematoda (roundworms)

3. Shape of Life Video: Annelids

4. 3 Major Classes in Phylum Annelida
Class Oligochaeta: the earthworms
Class Hirudinea : The leeches
Class Polycheata: The marine worms

5. Identifying Characteristics of the Annelids
Group of soft-bodied animals commonly known as segmented worms
Segments are separated internally into compartments by septa
Segments are marked by little rings called annuli (annulus = little ring)

6. Identifying Characteristics of the Annelids
Bilateral symmetry
Triploblastic (three tissue layers)
TRUE COELOM (body cavity which allows them to have true organ systems and muscular layers)
Possess complex digestive & circulatory systems
Nervous and excretory systems
No developed respiratory system as they exchange O2 and CO2 via moist epidermis. Aquatic worms may exchange gases through gills.

7. Identifying Characteristics of the Annelids
Mostly free-living heterotrophs
Terrestrial, freshwater and marine environments
Mostly aquatic or damp environments
Many annelids are nocturnal
Can range in size from less than 1 mm to over 3 meters (the seep tube worm)

8. Identifying Characteristics of the Annelids
Reproduce sexually and some asexually by regeneration and fission
Are hermaphroditic with cross fertilization

9. Example: The Earthworm
Digestive system: one way tube including: mouth/pharynx, anus and specialization of digestive organs (esophagus, crop, gizzard, and intestines)
Earthworm feces (castings) act as fertilizer

10. Typhlosole increases surface area for digestion
Food moves through digestive tract from mouth to anus due to peristalsis (rhythmic muscular contractions)

11. Circulatory system
Closed system (blood contained in vessels)
Dorsal vessel, ventral vessel, ring vessels connect segments. Valves prevent backflow.
Presence of a primitive heart (actually 5 aortic arches) to pump blood

13. Nervous system
cephalization and primitive brain
ventral nerve cord
no defined sensory organs

14. Excretory system
nephridia (primitive kidneys) which eliminate waste from blood and expel it from body (via nephridiopore). One pair of nephridia per segment.

16. Movement Hydrostatic skeleton Circular and longitudinal muscles
Setae anchor the earthworm during movement

17. Response
Most annelids are active animals with well developed nervous systems
Brain sits on top of the gut at the anterior end
Ventral nerve cord
Earthworms have no defined sensory organs
Light sensitive skin

18. Reproduction
As always, variety seen within a large group of organisms!
Most annelids reproduce sexual
Some can reproduce asexually by budding or regeneration
Most annelids are hermaphroditic
Some species have separate sexes and external fertilization

19. Earthworm Reproduction http://www.youtube.com/watch?v=2fG-KkR3FZ8
Hermaphroditic: (produce both eggs and sperm)
must still copulate in order to mix their gametes (cross-fertilization)
Regeneration: capable of re-growing amputated segments of their bodies
Mating Earthworms

20. Earthworm Reproduction
When two earthworms do mate they release sperm to one another.
Each earthworm’s seminal receptacle receives sperm from its mate’s seminal vesicles.
Sperm and eggs are released into the cocoon secreted by the clitellum
Fertilization is external

21. Worm Clitellum

24. Organization 3 Classes Class Polychaeta Class Hirudinea Marine worms
Parapodia
Paired appendages on each segment
Trochophore larvae
Class Hirudinea
Leeches
Mostly freshwater
Free-living or ectoparasites

25. Organization Class Oligochaeta Ex. earthworms, etc.
Freshwater or terrestrial
Each segment contains 4 sets of bristles called setae
Light sensitive epidermis
Body adapted for burrowing
Reduced head
Streamlined body

26. Other Annelids: Class Polychaetes
Marine worms
Parapodia (pad-like appendages with bristles)
Live in coral reefs, sand, mud, crevaces

27. Nervous systems in Marine species
Sensory tentacles
Chemical receptors
Two or more pairs of eyes

28. Class Hirundinea: Leeches
Mostly ectoparasites (external parasites)
Drink blood and body fluids of host
About 25% of leeches are free-living carnivores
Eat snails, worms, insect larva

29. Take Two Leeches and Call Me in the Morning

30. Kingdom of the Leeches

31. Ecological Importance of Annelids
Form the base of many food chains
House (carry) parasites such as Protozoa, Platyhelminthes and Nematodes
Aerate & mix the soil and are constructive to mineralization and nutrient uptake by vegetation
Certain species mix the nutrient-rich surface and mineral soil by traveling between the two
Oligochaete Worm

32. Chemical Roles include:
Biological Roles:
composters
help integrate dead organic matter to make fertile soil
Chemical Roles include:
help cycle nutrients and minerals through the soil through their casts (worm poop!)
Increase the levels of nitrogen, phosphates and potash

33. Physical Roles include:
burrowing and keeping the soil structure open (aerating the soil and providing a path for drainage)

34. Random Annelid Facts
In the New Zealand Maori culture NOKE is an earthworm dish sold as a delicacy
Lumbriculus and Aulophorus (species of annelids) are known to reproduce by the penis breaking into fragments and then forming whole new worms!

35. Australian giant earthworm

36. Annelids http://www.youtube.com/watch?v=NxeT_GDKv9g