+General Annelid Characteristics
- Coelomate, Triploblastic
- Protostome (lophotrochozoan)
- Bodies are segmented, worm-shaped
- Setae (chaetae)
- Closed circulatory system
- Complete digestive system
- Marine, freshwater, terrestrial
+Class Polychaeta (nearly all marine)
+ Parapodia function in locomotion and gas exchange, are highly vascularized and increase the surface area of the body wall. (Many Setae)
– Subclass Oligochaeta (mostly terrestrial or freshwater)
Anatomy of an Earthworm
+ They have a closed circulatory System, complete digestive Tract and exhibit cephalization.
+ Earthworms play an essential role in aerating the soil and in adding nutrients.
+ They are Metanephridia so they have a tube open at both ends.
+ Oligochaetes have no specialized respiratory structures. (simultaneous hermaphrodites)
Subclass Hirudinea (mostly freshwater, terrestrial)
• No setae or appendages
• Anterior and posterior suckers
• Few body segments – 33- 34, more flattened dorsoventrally
• No internal septa
• Many are Ectoparasites
+ Many have an extendable proboscis with chitinous jaws/teeth.
+ Arenicola, a deposit feeder, sedentary polychaete which burrows in soft sediments.
+ Feather Duster Worm is a marine polychaete.
+ Regeneration and asexual reproduction in some Polychaetes