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1. 02 April 2012 Annelida.ppt 1 Phylum Annelida “segmented worms”
2. 02 April 2012 Annelida.ppt 2 Phylum Annelida ~ 9000 species
Segmentation highly developed
Mesodermal “blocks,” each with own coelom
Septa between segments
3. 02 April 2012 Annelida.ppt 3 Phylum Annelida Hydrostatic skeleton
Fluid pressure in coelom provides support & locomotion
Circular muscles
Longitudinal muscles
Peristaltic locomotion
4. 02 April 2012 Annelida.ppt 4 Function of a hydrostatic skeleton
5. 02 April 2012 Annelida.ppt 5 Phylum Annelida Setae (“bristles”) of chitin
“anchors” for earthworm
“paddles” for polychaete
Enlarged as jaws in leeches, some polychaetes
6. 02 April 2012 Annelida.ppt 6 Phylum Annelida Closed circulatory system
Multiple “hearts”
Hemoglobin not in blood cells
reddish-pink color
7. 02 April 2012 Annelida.ppt 7 Phylum Annelida Central nervous system
Dorsal brain
Pair of nerves on sides of esophagus
Paired ventral nerve cords with paired ganglia in each segment
Transverse nerves connect ganglia in each segment
8. 02 April 2012 Annelida.ppt 8 Phylum Annelida Earthworms’ paired nerve cords are fused into single ventral cord
Arthropod better illustrates primitive nervous system of both phyla.
9. 02 April 2012 Annelida.ppt 9 Phylum Annelida Class Polychaetes
“many setae,” clusters with 20+ setae
parapodia
10. 02 April 2012 Annelida.ppt 10 Phylum Annelida Class Earthworms
few setae in 2-4 clusters per segment
Clitellum
11. 02 April 2012 Annelida.ppt 11 Phylum Annelida Class Leeches
pair of bladelike “jaws”
posterior “suction cup”
Predators
External parasites, “bloodsuckers”
Secrete anticoagulants
Medicinal use
12. 02 April 2012 Annelida.ppt 12 Phylum Annelida Leeches
Hirudin from leech, Hirudo medicinalis, inhibits blood clotting