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Phylum Annelida

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Phylum Annelida

  • Traits
    • Coelomate
    • Closed circulatory system
    • Complete digestive System
    • Cephalization
    • Segmentation
      • Metameres
      • Septa
    • Setae
      • Bristles

Spirobranchus giganteus�Christmas tree worm

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Annelid Body Plan

Setae

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Annelid Taxomony

  • Class Polychaeta (many bristles)
    • most numerous species
    • marine

Hermodice crunculata

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Annelid Taxomony

  • Class Polychaeta
  • Class Oligochaeta (few bristles)
    • Freshwater, marine & terrestrial

Lumbricus terrestris

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Annelid Taxomony

  • Class Polychaeta
  • Class Oligochaeta
  • Class Hirudinea
    • Internal and External Segmentation
    • Setae absent

Hirudo medicinalis

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Class Polychaeta

  • Highly specialized head �regions
    • Antennae
    • Sensory palps
    • Feeding appendages
  • Parapodia
  • Often tube-dwelling

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Bispira bunnea

sabellid worm

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Polychaete Anatomy

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Polychaete Anatomy (cross section)

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Respiratory and Circulatory Systems�

  • Gases are exchanged by diffusion through the body wall
  • Closed circulatory system
    • Dorsal aorta
    • Ventral aorta
    • Capillaries in parapodia

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Polychaeta

Amphitrite

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Polychaeta

Lugworm (Arenicola sp)

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Polychaeta

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Polychaeta

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Clade Siboglinidae �

Ridgea sp

Riftia pachyptila

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Giant tube worms (Vestimentifera)

Riftia pachyptila

trophosome

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Polychaete Reproduction

  • Regenerate lost parts easily

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  • Dioecious
  • Free-swimming larvae

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  • Some species develop specialized �segments containing gametes

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Class Oligochaeta

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Oligochaete Anatomy

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Oligochaete Anatomy

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Seta: a.k.a. Bristles

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Oligochaete Excretory System

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Oligochaete Nervous System

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Oligochaete Nerve Cord

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Oligochaete Reproduction

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Common Terrestrial Oligocheates: Earthworms

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Not all earthworms are small and boring…

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Quick and Easy Earthworm Morphology Guide

Morphology

Number & location of GTs and TPs, location & shape of clitellum

Ecology

Location of burrows

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Aporrectodea turgida

Lumbricus rubellus

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Aquatic Oligocheates

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Class Hirudinea

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Hirudo medicinalis

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  • Defining characteristics
    • Posterior sucker
  • Predominately freshwater, but do occur in all seas and moist soil
  • Leeches can swim or crawl using sucker and longitudinal muscles

Phylum Annelida

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Leech Anatomy

  • Anterior sucker is small and contains the mouth
    • Creates a wound with saw like jaws
  • Leeches drink other animals’ blood, usually vertebrates
    • Carnivores

or

    • Scavengers

Phylum Annelida

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Blood Sucker

  • The salivary glands excrete hirudin which prevents the blood from coagulating
    • May also secrete an anaesthetic and substance to dilate small blood vessels
  • Blood is broken down by symbiotic bacteria that is then used by the leeches
  • Leeches were commonly used in the 19th century for bloodletting
    • Recent medical uses are to relieve pressure after vascular tissue is damaged
      • Snake bites or the reattachment of a finger or ear

Phylum Annelida

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Earthworms vs Leeches

http://www.diffen.com/difference/Earthworm_vs_Leech