1413 Presentation

1. Annelida

3. Phylum Annelida
Diversity - 15,000 species (Hickman et al. 2017)
- Taxonomy is a mess!
- Historically grouped into 3 classes
- Polychaeta - polychaete worms
- Oligochaeta - earthworms and allies
- Hirudinida - leeches

4. Phylum Annelida
Diversity - 15,000 species (Hickman et
al. 2017)
- Taxonomy is a mess!
- In truth, the leeches arose within
the oligochaetes
- And the oligochaetes arose within
the polychaetes

5. Phylum Annelida

6. Phylum Annelida

7. Phylum Annelida

8. Phylum Annelida
General features
- Eucoelomate
- Protostomes
- Spiral cleavage
- Segmented
- metamerism
- Annuli mark segments
- Delimited internally by septa
- Setae present (generally)

9. Phylum Annelida
Body Plan
- All elongate
- Two-part head
- Prostomium and peristomium
- Segmented body (trunk)
- Pygidium bearing anus

10. Phylum Annelida
Body Plan
- Non-chitinous cuticle covers body
- Parapodia may be present
- Lateral flaps on segments
- Coelom walled off by peritoneum
- Hydrostatic skeleton created by
coelomic fluid

11. Phylum Annelida
Two groups
- Errantia - free moving; highly active
- The familiar polychaetes (polychaete
observation from lab)
- Sedentaria - sessile or mostly so
- All other annelids

12. Phylum Annelida
Twp groups
- Errantia - free moving; highly active
- The familiar polychaetes (polychaete
observation from lab)
- Sedentaria - sessile or mostly so
- All other annelids

13. Phylum Annelida
Errantia
- Motile polychaetes
- Mostly marine
- 5-10 cm in length (may be 3m!)
- Brightly colored or dull
- Reclusive
- Well developed head
- Parapodia present
- Setae are numerous
- Clitellum lacking

14. Phylum Annelida
Errantia
Form and function
- Prostomium
- Overlies the mouth
- Eyes, tentacles, and sensory palps
- Peristomium
- Surrounds the mouth
- Setae, chitinous jaws, tentacles

15. Phylum Annelida
Errantia
Form and function
- Trunk
- Segmented with parapodia
- Used in locomotion
- Primary respiratory organ
- Many setae
- May be divided into notopodia and
neuropodia

16. Phylum Annelida
Errantia
Nutrition
- Usually predators or scavengers
- Foregut
- Acquisition of food
- Midgut
- Digestion of food
- Hindgut
- Absorption of nutrients
Errantia
Circulation and Respiration
- Circulation may be open or closed
- Coelomic fluid may assist in transport
- Parapodia, gills, and cutaneous respiration
are all known
- Diverse

17. Phylum Annelida
Errantia
Excretion
- Most with metanephridia
- Some with protonephridia and
metanephridia
- One pair per segment
Errantia
Nervous system
- Dorsal cerebral ganglia
- Ventral nerve cord
- Highly developed sense organs
- Eyes
- Photoreceptors
- Complex
- Nuchal organs
- chemoreceptive
- Statocysts

18. Phylum Annelida
Errantia
Reproduction
- Permanent sex organs lacking
- Clitellum lacking
- Typically dioecious
- External fertilization
- Trochophore produced
- Some unique strategies
- Atokes and epitokes

19. Phylum Annelida
Sedentaria
- More sessile or sessile polychaetes
- Many that live in burrows
- Oligochaetes
- Leeches
- Much of the body plan is similar to
Errantia
- Except, head often modified with
tentacles used in food capture

20. Phylum Annelida
Sedentaria
Tubeworms
- Secrete the tube they live in
- May be papery or leathery
- Most are particle feeders
- Ciliary and deposit feeders

21. Phylum Annelida
Clade Clitellata
- Earthworms and allies in Oligochaeta
- Leeches in Hirudinida
Share clitellum, a ring of secretory cells in the epidermis
- Always visible in oligochaetes; only visible during reproduction in leeches
Lack parapodia
All monoecious and have direct development

22. Phylum Annelida
Oligochaetes
- Not a monophyletic group (paraphyletic)
- Mostly terrestrial and freshwater
- Some are marine
- Setae are present, but always few

23. Phylum Annelida
Oligochaetes
- Form and function
- Locomotion - circular and longitudinal
muscles contract to change the shape
of segments
- Shortening pushes sete from
body - allows for grip against soil

24. Phylum Annelida
Oligochaetes
- Form and function
- Nutrition - most are scavengers
- Mouth moistens food and pharynx
draws it in
- May ingest excess soil
- Calciferous glands help rid the
body of excess calcium ions
- Food is stored in crop, then transported
to gizzard for grinding
- Typhlosole enhances surface area
- Chloragogen cells (tissue) serves as
liver

25. Phylum Annelida
Oligochaetes
- Form and function
- Circulation - both coelomic fluid and
and fluid of a closed circulatory system
aid in transport
- Dorsal vessel pumps blood anteriorly
- Ventral vessel pumps posteriorly
- Five aortic arches help maintain
blood pressure
- Hemoglobin used for respiratory
pigment

26. Phylum Annelida
Oligochaetes
- Form and function
- Respiration
- No dedicated organ
- All done through cutaneous
respiration

27. Phylum Annelida
Oligochaetes
- Form and function
- Excretion - metanephridia
- Each segments bears a pair
- At opening is nephrostome
- Lies in segment anterior to
metanephridia
- Posterior of nephrostome is
convoluted tube ending in a
nephridiopore

28. Phylum Annelida
Oligochaetes
- Form and function
- Nervous system and sense organs
- Both CNS and PNS
- CNS has paired ganglia above
pharynx
- Sense organs are distributed
throughout the body
- photoreceptors and
chemoreceptors

29. Phylum Annelida
Oligochaetes
- Reproduction
- Monoecious
- Practice cross-fertilization
- During copulation, clitella secrete
mucus that hold animals together
- Sperm travel to seminal vesicles via
seminal groove
- Clitellum secretes a cocoon
- Cocoon collects eggs, albumen,
and sperm
- Deposited in moist soil

30. Phylum Annelida
Hirudinida
- Number of segments is fixed within a class
- Predominantly freshwater
- Few are marine, few are terrestrial (moist and humid habitats only)
- Generally small (2 - 6 cm)
- Dorsoventrally flattened
- All monoecious
- Clitellum present
- Many are predaceous, only some are temporary parasites

31. Phylum Annelida
Hirudinida
Form and function
- False annuli give appearance of
many more segments
- Distinct coelomic compartments are
lacking
- Septa are absent from all but one
species
- Suckers are generally present at
oral and posterior end
- Crawl in inchworm fashion

32. Phylum Annelida
Hirudinida
Nutrition
- Fluid feeders
- Even if predaceous
- Parasites have cutting plates
- Anesthetic and anticoagulant enzymes

33. Phylum Annelida
Hirudinida
Respiration and Excretion
- Gas exchange through skin in
most
- Parasites of fish have gills
- 10-17 pairs of nephridia
Hirudinida
Nervous system
- Two “brains”
- One anterior and one posterior
- Photoreceptors and sensilla
present

34. Phylum Annelida
Hirundinidae
- Reproduction
- Monoecious
- With cross-fertilization
- Sperm transferred by penis
- Hypodermic impregnation in some
- After copulation, clitellum secretes a
cocoon
- Development is direct

35. Phylum Annelida
Hirundinidae
- Circulation
- Highly variable
- Some have dedicated vessels like the oligochaetes
- Others only have sinuses within the body
- Serve as an open circulatory system