1. MARINE WORMS

2. Common Characteristics of All Worm Phyla
Hydrostatic skeleton
Bilateral symmetry

3. Phylum Platyhelminthes - Flatworms
Dorsoventrally flattened – flat backs and bellies
Have real organs and organ systems
Ladderlike nerve cord with a simple brain
Saclike digestive system (only one opening)
15,000 species
Turbellarians – mostly free swimming carnivores
Flukes (trematodes) – all are parasites
Tapeworms (cestodes) – parasites with long segmented bodies

4. Phylum Nemertea – Ribbon Worms
Long flattened bodies
Complete digestive tract (separate mouth and anus)
Circulatory system with blood
Proboscis – long fleshy tube used to entangle prey
900 species, mostly marine

5. Phylum Nematoda - Roundworms
Common in sediments or as parasites
Cylindrical body typically pointed at both ends
Complete digestive tract
10,000-15,000 species but many could yet to be discovered

6. Phylum Annelida – Segmented worms
13,000 species
Complete digestive tract
Efficient crawlers and burrowers
Closed circulatory system – blood always remains in blood vessels (arteries, veins, capillaries)
Class Polychaeta
On each segment they have a pair of parapodia and setae (bristles)
Gills for respiration
6000 species almost entirely marine

7. Class Hirudinea – Leeches
4 to 10 cm in length
Deposit or suspension feeders
Some are tube dwelling
Class Hirudinea – Leeches
Mostly freshwater
Suckers at each end
No parapodia

8. Other Marine Worms Phylum Sipuncula – Peanut worms Phylum Echiura
Peanut shaped, deposit feeders
Phylum Echiura
Sausage shape, buried in mud
Phylum Pogonophora – Beard Worms
Lack a digestive system, symbiotic relationship with bacteria for obtaining nutrients
Vestimentiferans found at hydrothermal vents
Phylum Chaetognatha – Arrow Worms
60 species, but common in plankton, fishlike body, voracious carnivores