Phylum Annelida Segmented body metamerism Setae Absent in

Phylum Annelida • Segmented body – metamerism • Setae – Absent in leeches • Eucoelom divided by septa • Closed circulatory system • Nephridia for each segment 2

Metamerism

6

Class Polychaeta Parapodium Head Tentacle 7

Trochophore larva Apical tuft Stomach Ciliary band Mouth Anus

Aphroditidae (sea mouse)

Capitellidae 10

Sabellidae 12

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Marine leech Gill

Hirudo medicinalis

Haemadipsa sp.

Pygidium Septa Prostomium Peristomium Mouth 22

Setae (Chaetae) • Chitin 23

25

Genital papillae

27

Epidermis Circular muscle Longitudinal muscle cuticle Peritoneum

4 3 5 2 1 7 31

1 2 4 5 6 7

E

Chloragogen cells Typhlosole Ventral nerve cord

Lateral neural vessel 38

Aortic arches Dorsal vessel

Dorsal vessel Ventral nerve cord Ventral vessel

Mesentery Ventral vessel Lateral neural vessel Subneural vessel

43

Nephridia

nephrostome (nephridiopore)

Dorsal vessel Nephridial bladder Nephridiopore Nephrostome 46

Brain Circumpharyngeal connection Subpharyngeal ganglion Ventral nerve cord 48

49

55

Cocoon