Annelids

1. Annelids Study Dissections Lab Notes

2. Annelid Characteristics • Well developed true coelom • Segmented (reduced or lost in some) • Complete digestive tract with regional specialization • Closed circulatory system with respiratory pigments • Well-developed nervous system • Usually with lateral chaetae (setaes) on each segment • Marine, fresh water, and terrestrial environments

3. Class ClitellataSubclass Oligochaeta • Characteristics • Few chaetae (setae); lack parapodia • Little structural specialization of head • Presence of clitellum (forms muscus and egg cocoon) • Mostly in terrestrial or fresh water environments

4. Lumbricus terrestris • Earthworm (Night Crawler) dissection follows on the next set of slides

6. Nephridia Ventral nerve cord

9. Aortic arches

10. Seminal receptacles

12. Nephridia nerve cord

17. Class ClitellataSubclass Hirudinoidea - Leeches • Segmenting less defined; body not divided by septa • Clitellum present • Lack setae or parapodia • Have a posterior sucker and usually also an anterior sucker • Mostly in fresh water, a few are marine and semi-terrestrial • May be scavengers, predators, or external parasites

19. Class Polychaeta • Numerous chaetae (setae) on segments • Most have parapodia • Often with tentacles, sensory, or feeding structures on head • Some have chitinous jaws • Lack clitellum • Mostly marine; burrow, crawl over substrates, or live in tubes • This class may be paraphyletic

20. Neries The Clam Worm