1. Phylum Annelida the segmented worms
1st phyla we will talk about and what we will cover in the lab today is…
the segmented worms

2. Phylum Annelida
Annelida from the Latin word annelus meaning “little ring”
All are segmented worms
Approximately 15,000 species including earthworms, freshwater worms, leeches, and marine worms

3. Annelida Characteristics
Triploblastic- 3 cell layers
Highest level of organization: organs
Bilateral Symmetry
Cephalization
Eucoelomate

4. Body Cavity Eucoelomate
Have a “true” body cavity that is completely surrounded by mesoderm
ectoderm
coelom
mesoderm
Gut
endoderm

5. Annelid Characteristics
the coelom
is a closed, fluid filled cavity that surrounds the gut
the fluid within acts as a circulatory system (blood)
tissue membranes (mesenteries) suspend organs in the coelom
ectoderm

6. Annelida Characteristics
Metamerism
The body is made up of a series of repeating, coordinated segments called metameres that are separated from one another by septa.
Each metamere contains sets of repeating organs
e.g. gut, blood vessels, nerve cord, excretory organs

7. Metamerism
septa

8. Metamerism

10. Annelid Characteristics
Two part head consisting of
Prostomium: fleshy lobe that overhangs the mouth
Peristomium: first body segment
Annuli: circular rings
Pygidium: the last segment; where the anus is
Clitellum: reproductive structure
annuli

11. pygidium

12. Annelida Characteristics
Nervous system
2 cerebral ganglia
a ventral nerve cord with 2 ganglia per metamere.
In some species, sensory organs such as eyes, palps, and tentacles have arisen
(palps are appendages that may or may not be covered in cilia that help the worm find and pull in food)

13. Annelida Characteristics
Locomotion
both longitudinal and circular muscles which allow them to “wiggle”
most have setae (chitonous bristles secreted by the epidermis) that aid in locomotion and burrowing
Skeletal System
fluid in coelom acts as a hydrostatic skeleton

14. Annelid Characteristics
Gas exchange
mainly by diffusion through skin
Class Polychaeta often has specialized structures for gas exchange
(e.g. parapodia, gills)

15. Annelid Characteristics
Digestive System
unidirectional
regional specialization (digestive organs)
Circulatory System
closed circulatory system composed of blood vessels (some of which are contractile and act as “hearts”)
some circulation is also accomplished by the coelomic fluid

16. Annelid Characteristics
Excretion
excretion is accomplished by organs called nephridia (singular nephridium)
sexual
Reproduction

17. Phylum Annelida
Class Polychaeta
Class Oligochaeta
Class Hirudinea

18. Class Polychaeta
1st phyla we will talk about and what we will cover in the lab today is…

19. Class Polychaeta All marine
This class contains 2/3 of all known Annelids
Common species are clamworms, sandworms, and lugworms
have a well developed head with specialized sense organs
1st phyla we will talk about and what we will cover in the lab today is…

20. Class Polychaeta Commonly called “bristle worms”
Have many setae (chitonous bristles secreted by the epidermis)
(Poly = many, chaeta= setae)
These setae are arranged in bundles on paddle-like appendages called parapodia
1st phyla we will talk about and what we will cover in the lab today is…
setae

21. Class Polychaeta
Parapodium
1st phyla we will talk about and what we will cover in the lab today is…
setae
The parapodia function in gas exchange, locomotion, and feeding.

22. Class Polychaeta Tagmatization (tagmosis)
the fusion and specialization of formerly metameric segments
1st phyla we will talk about and what we will cover in the lab today is…

23. Class Polychaeta Many are filter-feeders with specialized structures
1st phyla we will talk about and what we will cover in the lab today is…

24. Class Polychaeta Many are predatory with specialized structures
1st phyla we will talk about and what we will cover in the lab today is…

25. Class Polychaeta
1st phyla we will talk about and what we will cover in the lab today is…
Many construct their own homes out of CaCO3 or sand debris and mucous

26. Class Polychaeta Reproduction
Usually dioecious (separate male and female)
No permanent sex organs; gametes are shed into coelom where they stay until time for fertilization
Fertilization is usually external in water
Indirect development  trocophore larvae swims around until it grows into adult form by adding segments
1st phyla we will talk about and what we will cover in the lab today is…

27. Ecology Polychaetes often have effective defense strategies:
some have tubes to hide in
some have vicious jaws
some have modified “stinging” setae
1st phyla we will talk about and what we will cover in the lab today is…
a fireworm

28. Ecology
Some Polychaetes have a mutualistic relationship with their host
for example, many scaleworms are found near, or in the mouth, of brittlestars, starfish, and sea urchins.
The scaleworm eats its host’s leftovers and with its vicious jaws, it will attack any predator trying to eat it’s host.
1st phyla we will talk about and what we will cover in the lab today is…

29. Class Oligochaeta
1st phyla we will talk about and what we will cover in the lab today is…

30. Class Oligochaeta Habitats: terrestrial, freshwater, and marine
Have few setae (Oligo = few, chaeta = setae)

31. Class Oligochaeta What do earthworms eat? Usually feed on detritus
(decaying organic matter)
Depends on habitat, but they can feed on…
Dead leaves and plant roots
Living things such as other worms, bacteria, and fungi
Decomposing remains of other animals

32. Class Oligochaeta Do earthworms eat dirt? Yes and No.
Earthworms consume dirt as they burrow, so yes they do swallow it.
HOWEVER, they do not get nutrients from the dirt. Their nutrients come from decaying plant and animal remains that are in the dirt.

33. Class Oligochaeta
Earthworms have specialized digestive system to obtain the maximum amount of nutrients out of the detritus.
Example: pharynx, crop, gizzard, etc.

35. Class Oligochaeta Locomotion Circular muscle contraction
Longitudinal muscle contraction

36. Class Oligochaeta Reproduction Usually monoecious
Still have to have a partner.
Cross-fertilize by
exchanging sperm
clitellum
testis

37. Ecology
Earthworms are essential soil aerators, meaning they allow air to enter the soil.
Mix the soil with their tunnels.
Worm feces are great plant food = fertilizer!
1st phyla we will talk about and what we will cover in the lab today is…

38. Class Hirudinea
1st phyla we will talk about and what we will cover in the lab today is…

39. Class Hirudinea Includes leeches
usually freshwater but there are some marine and terrestrial species
no septa between metameres
no setae or parapodia
have 2 suckers

40. Class Hirudinea
have an extendable proboscis for feeding

41. Class Hirudinea usually have a fixed number of segments (34)
each metamere consists of several annuli (think accordion)
1 metamere
annuli

42. Class Hirudinea Locomotion
Lack septa between metameres, so they are incapable of moving like Oligochaetes.
Instead, they use their anterior and posterior suckers to move.
1st phyla we will talk about and what we will cover in the lab today is…

43. Class Hirudinea Reproduction usually monoecious cross-fertilize by
exchanging sperm
1st phyla we will talk about and what we will cover in the lab today is…

44. Ecology
Although some leeches are parasitic blood suckers (can be temporary or permanent), many are predators.
1st phyla we will talk about and what we will cover in the lab today is…

45. Ecology Leeches have been used medicinally since the 19th century.
Currently they are used to increase blood flow following reconstructive surgery
Hirudin is a powerful anticoagulant that is found in the salivary glands of leeches
1st phyla we will talk about and what we will cover in the lab today is…