Annelids

1. Annelids

2. Phylum Annelida Class Aelosomata Class Polychaeta Class Clitellata Aelosomata Marine worms Subclass Errantia Subclass Sedentaria Subclass Oligochaeta Subclass Hirudinae earthworms Leeches

3. Annelids • Class Polychaeta • marine worms • segmented • Class Clitellata • Subclass Oligochaeta • earthworms • segmented • Subclass Hirudinea • Leeches • segmented

4. Characteristics • Segmentation (metameric body plan) • Eucoelomate • 15,000 species • Closed circulatory system, but no heart • Hydrostatic skeleton • Excretion- protonephridia, metanephridia, diffusion or gills • Simple gut • Respiration- diffusion or gills • Central nervous system- brain and nerve cord • Reproduction- asexual or sexual (many gonochoric) • Sensory system of tactile organs, taste buds, statocysts,photoreceptor cells, and eyes with lenses.

5. Subclass Oligochaeta • Lack parapodia and have few setae • Lack the distinctive head region of polychaetes and have no eyes. • Scavengers that consume soil that contains organic matter • The ingested soil moves into a storage chamber called the crop, then to an area called the gizzard, where grinding action breaks down the soil particles. Undigested material passes out the anus in a form called castings, which are prized as soil fertilizer.

6. Metamerism (segmentation) • Each segment is also known as a metamere • Each metamere has a parapodia with numerous setae parapod chaetae

7. gut Body Cavities Mesoderm coelom Eucoelomate- body cavity completely lined with mesoderm Ectoderm Endoderm

8. Hydrostatic Skeleton EarthwormPhylum Annelida

9. Closed Versus Open Circulatory Systems

10. Closed Circulatory System

11. Nervous System and Behavior • A mass of ganglia (neural masses) forms an anterior brain that is usually dorsal to thepharynx. • They have either a pair of ventral nerve cords(primitive) or a single ventral nerve cord that runsthe length of the body. • Each segment has a swelling of the nerve cord called a segmental ganglion. • Sensory receptors include: chemoreceptors, touchreceptors, photoreceptors, statocysts and vibration receptors. • Behaviors vary depending on class/life style.

12. Oligochaete Nervous System

13. Digestive System Esophagus Gizzard Pharynx Crop Buccal cavity Intestine Mouth

14. Reproductive System Seminal vesicle Ovary Testes Egg funnel and oviduct Sperm duct Seminal receptacle

15. Oligochaete Reproduction

16. Oligochaete Excretory System

17. Subclass Hirudinea • Leeches • Most live in fresh bodies of water, but some live among moist vegetation. • Suckers found on both ends • Unlike other annelids, its segments are not separated internally • Leeches lack both setae and parapodia • Most are predators or scavengers. Very few are parasites. • They secrete anticoagulants, hirudin, to keep blood from clotting and anesthetic that prevents the host from feeling their presence.

18. Subclass Hirudinea

19. Hirudo medicinalis

20. Class Polychaeta • Largest group of annelids • Primarily marine • Most segments include a pair of paddle–like parapodia • Well-developed head with eyes and other sensory structures

21. Class Polychaeta Subclass Sedentaria • Fan worms, • Christmas-tree worms • Spaghetti worms • Chaetopterus • lugworms • Subclass Errantia • Sand worms, • Scale worms • Fire worms • palolo worms

22. featherduster worms Subclass Sedentaria

23. Lugworm Subclass Sedentaria

24. Chaeopteris Subclass Sedentaria

25. Spaghetti worm Lanice conchilega • Hawaii has 11 species • 5 are endemic Subclass Sedentaria

26. Christmas tree worms Spirobranchus giganteus Subclass Sedentaria

27. Scale worm Subclass Errantia

28. Fire worm Eurythoe complanata Subclass Errantia

29. The pharynx is everted by contraction of body wall muscles.

30. Parapodia- movement and respiration

31. Polychaete Trochophore Larvae

32. Polychaete Larvae (setiger)