Annelids

Annelids are what kind of protosomes?

Lophotrochozoan

2 major clades in Annelids:

Our Annelid Classification:

Body Plan

• Nereis a good example (errant polychaete)

• Metamerism (segmentation)

• Head of prostomium, peristomium

• Tail of pygidium

• Parapodia (biramous)

• Setae/Chaetae

• closed circulatory system

• dorsal and ventral blood vessels, “hearts”

• ventral nerve cord

• metanephridium

• cutaneous/gill respiration

• sexual reproduction

Metamerism

each segment (“somite”) is its own hydrostatic skeleton • Septa between them • longitudinal and circular muscles act as antagonists • parapodia and setae used for locomotion & feeding

Errant Polychaetes (Subclass Errantia)

Includes: • Nereids (clam worms) • Polynoids (scale worms)

Predatory • senses well-developed • eversible pharynx with jaws

Sedentary Polychaetes (Clade Sedentaria & Subclass “Sedentaria”)

Tubeworms • e.g., featherduster worms (sabellids) • live in parchment tube • filter feed with radioles

Sedentary Polychaetes

Tubeworms • e.g., christmas-tree worms (serpulids) • live in calcareous tube

Amphitrite (terebellid) • “spaghetti worm” • tentacles extend across sand, sweep up food

Arenicola (lugworm) • Abarenicola

Echiurans (spoon worms) • proboscis with “gutter”

Sipunculans (peanut worms) • “introvert”

Pogonophorans (Siboglinids) • “Beardworms” or vestimentiferan tubeworms • Deep sea

Pogonophorans (Siboglinids) • “Beardworms” or vestimentiferan tubeworms • Deep sea, near “black smokers” • trophosome harbors chemoautotrophic bacteria

Class Clitellata: Subclass “Oligochaeta” (in clade Sedentaria)

freshwater & terrestrial • earthworm (Lumbricus) and blackworm (Lumbriculus) are good examples • Named for clitellum • Have few (oligo-) setae (-chaeta)

Clitellata: Oligochaete Anatomy • nervous system

Clitellata: Oligochaete Reproduction

Class Clitellata: Subclass Hirudinea (in clade Sedentaria)

Leeches! • Freshwater & Terrestrial • carnivorous & parasitic

• Medical leeches (Hirudo medicinalis)