Nematodes and annelids

1. WORMS
•Platyhelminthes
•Nematodes
•Annelids
Annelids

2. WORMS
•Platyhelminthes
•Nematodes
•Annelids
Annelids

4. Nematodes
What must I learn?
• Round worms: Cylindrical and soft body with tapered end,
not divided in segments.
• Most of them are free-living but some are parasitic and
responsible for many diseases. (Pinworm, anisakis, trichina)
• No respiratory system.

5. Nematodes
• Pinworms
– Adults reside in the large intestine.
– Enter humans by being eaten.
• Dracunculus
• Hookworms
– Adults live in the small intestine of humans.
– Enter host through the skin, usually between the toes. That makes you want to
walk around barefoot, doesn’t it?
• Anisakis
• Trichina
– Live in humans & other omnivores (like piggys)
– Adults live in the small intestine of it’s host; larvae encyst in the stomach and
skeletal tissue (ouch!). Enter host by being eaten.

6. • Picture of a male nematode.

7. M O V E M E N T
•No circular muscle in body
walls
•Longitudinal muscle flexion
combined with high internal
fluid pressure produces
whip-like wriggle

8. WORMS
•Plathyelminthes
•Nematodes
•Annelids
Annelids

10. Annelid Characteristics
• The phylum includes
polychaetes, earthworms
(Oligochaetes), and
leeches.
• Cutaneous respiration in
terrestrial and branchial
respiration in marine.
True segmented worms
• Metameric
segmentation

11. Polychaete

12. What do Oligochaetes look like?
Freshwater, very few marine and most terrestrial.
No parapodia.
Clitellum functions in reproduction.

14. How do Oligochaetes reproduce and develop?
Sexual
Mutual cross-fertilization.
Cocoon formed by clitellum.

15. Earthworm gathering

16. Class Hirudinea (Leeches)
• Predominately
freshwater, but do occur
in all seas and moist
soil
• Leeches do not burrow
or crawl, lack parapods
and setae
• Feed on blood

17. Leech