Phylum Annelida

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• McDougall ch. 23 annelids video• McDougall videos ch 14 symbitotic relationships

Annelids

• Annelids range in size from the Giant Earthworms, of which Michrochaetus rappi (Michrochaetus michrochaetus) is the largest• average length of 1.36 m (54 ins) and a record

breaking specimen has been recorded that measured 6.7 metres (22 ft) in length, it was 2cm (0.8 ins) in diametre.

• The smallest Annelid known to science is Chaetogaster annandalai • full grown at 0.5 mm (0.02 ins).

Phylum Annelida

• From the Latin Annellus a “little ring”. • Segmented body

•Metamere – segment in the body• Setae

•Small hair-like structures•Absent in leeches

• Coelom divided by septa •Separating tissue

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• Closed circulatory system•Have vessels and a pump

• Nephridia for each segment (metamere)•Excretory structures

• Nervous system – ganglia = brain; lateral nerve cords

• Reproduction•Most sexual•Some hemaphrodites

Phylum Annelida

Segmented Worms

• Body divided into repeating segments

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Metamerism

Setae – help in movement

ALL SEGMENTED WORMS are

EUCOELOMATES! “True coelom”

SEGMENTED WORMS (PHYLUM: ANNELIDA)

http://www.lander.edu/RSFOX/310images/310bilatImage.html10

SeptaSepta

MetamerismMetamerism

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Closed Circulatory System

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Ventral vesselVentral vesselVentral vesselVentral vessel

DorsalDorsalvesselvesselDorsalDorsalvesselvessel

BladderBladderBladderBladder

NephridioporeNephridioporeNephridioporeNephridiopore

NephrostomeNephrostomeNephrostomeNephrostome

Metanephridium – excretion of wastesMetanephridium – excretion of wastes

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Fig. 17.14

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Nervous SystemNervous System

Earthworm Reproduction

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Trochophore larvaTrochophore larvaApical tuftApical tuftApical tuftApical tuft

MouthMouthMouthMouth

AnusAnusAnusAnus

Ciliary bandCiliary bandCiliary bandCiliary band

StomachStomachStomachStomach

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Annelid developmentAnnelid development

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SEGMENTED WORMSAnnelida

FREE LIVING PARASITIC

Earthworms Leeches

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Sedentary/Sessile – don’t move

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Terrestrial

• Earthworm

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Feed on Blood

• Leech

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Class Polychaeta

• Many setae• Parapodia =

“paired feet”

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Class PolychaetaHeadParapodium

Tentacle

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JawJawJawJaw

Everted pharynxEverted pharynxEverted pharynxEverted pharynx

EyeEyeEyeEyeCirrusCirrusCirrusCirrus

PalpPalpPalpPalp

TentacleTentacleTentacleTentacle

ParapodiumParapodiumParapodiumParapodium

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• Polychaete Worm• Predatory

Nereis

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Class PolychaetaFireworm

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Sedentary Polychaete LugwormSedentary Polychaete Lugworm

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Pelagic* Polychaete

*Drift in the open ocean32

Just Slinking or Wriggling in the Rain

• Have you ever noticed that after a spring rain, earthworms come out of the soil and appear on driveways, in puddles, and on sidewalks? Why does this happen?

1. An earthworm breathes through its skin. If its skin dries out, it cannot breathe. Why would an earthworm be more likely to “surface” during the rain than at other times?

2. What types of weather conditions might be fatal for an earthworm?

Class Oligochaeta

• Few setae• Clitellum• No parapodia• Monoecious

•Both male and female parts

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Lumbricus terrestris - earthworm• Feed on decaying organic

matter• Enrich soil• Exceedingly important in

soil creation, particularly in temperate areas.

• Without them, agriculture and perhaps the whole of human society as we know it would never have evolved.

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• Return nutrients to soil by decomposing dead leaves and organic matter

• Burrowing allows air and water to penetrate to roots

• Tunnels loosen soil so roots can grow more easily

Earthworms play an important role in soil fertility

“intestines of the earth” -Aristotle

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External Structures of an Earthworm

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Section 27-3Anus

Clitellum

Circular muscle

Longitudinalmuscle

Nephridia Ganglia Ringvessels

Reproductiveorgans

Ventralblood vessel

Ganglion

Brain

Mouth

Dorsalblood vessel

CropGizzard

Body segments

Setae

The Anatomy of an Earthworm

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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Internal Structures of an Earthworm

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Body wallBody wall

EpitheliumEpitheliumEpitheliumEpithelium

Circular muscleCircular muscleCircular muscleCircular muscle

Longitudinal muscleLongitudinal muscleLongitudinal muscleLongitudinal muscle

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• Worms• Worms2

Class Hirudinea

• Anterior & posterior sucker

• No setae• Most live in fresh

water• Feed

•Invertebrates•Body fluids•Blood

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PARASITIC SEGMENTED WORMSLEECHES

Medical uses

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Man vs. Wild - Leeches

• Annelid• Annelid 3• Annelid 4

• Dirty Jobs – Bloodworms• http://www.youtube.com/watch?v=FX8DQ436F4g• Dirty Jobs worm grunting part 1• http://videos.howstuffworks.com/discovery/

38849-dirty-jobs-shorts-an-introduction-to-worm-grunting-video.htm

• Worm grunting part 2• http://www.yourdiscovery.com/video/dirty-jobs-

worm-grunting/• Earth watch – worm grunting• http://www.youtube.com/watch?v=D0YjFT8F7RU