• Segmented worms
• Bilateral symmetry
• Segments separated by septa
• Metamerism--repeating segments

Class Polychaeta

Characteristics

• Largests annelid class
• Diverse habitats
• Parapodia--flaps on segments
• Setae--hairlike extensions
• Metanephridia--excretion

Class Polychaeta

Nerius

• Clamworm
• Errant polychaet--wandering
• Jaws
• Nocturnal

Class Polychaeta

Spirobranchus

• Christmas tree worm
• Tube dwelling
• Sedentary

Class Polychaeta

Arenicola

• Lugworm
• Deposit feeder
• Lives in a U-shaped borrow
• Peristalsis--current
• External gills

Class Polychaeta

Aphrodita

• Sea mouse
• Covered in setae
• Photonic crystals
• Studied for fiberoptic communicaiton

Class Polychaeta

Hermodice

• Fireworms
• Setae have toxins
• Feed on corals

Class Polychaeta

Beardworms

• Live in hydrothermal vents
• Oxidize H₂S via bacteria--chemosynthesis

Class Polycheata

Palolo worm

• Atoke--immature
• Epitoke--mature, gamete production
• Rich food souce
• Example of swarming

Class Polychaeta

Reproduction

• External fertilization
• Trochophore larva
• Swarming--coordinated mass spawning

Class Hirudinea

Leeches

• FW, marine, terrestial
• Ectoparasites--blood suckers
• Secrete hirudin--antocoagulant
• No parapodia or setae
• Hermaphrodites
• Fixed number of segments
• Suckers on head and tail end

Class Oligochaeta

Earthworms

• Mostly FW
• Lack parapodia
• Cuticle
• First segment--Prostomia

Class Oligochaeta

Internal anatomy

• Feeding--mouth, pharynx, esophagus, crop, gizzard,intestine, anus
• Closed circulatory system
• Gas exchange through skin
• Nervous system--cerebral ganglia, nerve cords

Class Oligocheata

Reproduction

• Hermaphrodites
• Cross fertilization
• Clitellum produces cacoon for eggs

Class Oligochaeta

Excretion

• Paired metanephridia--1 pair per segment
• No flame cell
• Nephrostome--ciliated funnel
• Capiary bed
• Tubules open at both ends
• Nephridiopore--excretory pore

Class Oligochaeta

FW oligochaetes

• Stylaria--Prostomium drawn out into snout, prominant setae
• Tubiflex--Live in tubes, anoxic water habitat, causes whirling disease in trout