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Phylum Annelida:
Segmented Worms
• Body divided into
repeating segments
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1.
Annelida: annulus- ring, annual
2.
Body appears to be divided into
segments
metamerism- each segment
contains body systems, excretory,
circulatory, nervous, digestive
3.
Bilateral symmetry
4.
5.
two body openings (mouth & anus)
“ True” Eucoelomates-
6.
Live in every environment
7.
Reproduce sexually
(hermaphrodites)
8.
Setae- hair or bristles- except for
leeches
9.
Examples: bristleworms,
earthworms, leeches
Phylum
Annelida
Body Systems
• No Respiratory- gas
exchange through
skin
• *Circulatory
• Complete Digestion
• Nervous
• Muscular
• Excretory
• Reproductive
* Circulatory System
• Closed – blood always in
closed vessel
• Five pairs of aortic
arches(hearts)
• Ventral and dorsal blood
vessels and capillaries
• Hemoglobin
Digestive system
•
•
•
•
Crop-”stomach”- stores food
Gizzard- grinds food
Intestine- nutrient absorption
anus
Nervous System
• Pair of cephalic
ganglia(bundle of
nerves)
• Ventral nerve cord with
ganglia in each segment
(segmental ganglia)
Muscular System
• Longitudinal and
• Circular muscles
• Allows for better
movement- can
thrash and inch,
raise head, etc.
Body wall
Epithelium
Circular muscle
Longitudinal muscle
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Excretory System
• Wastes processed
through two
nephridia(kidney) in
each segment
• Nephridia, bladder
and excretory pore
Fig. 17.14
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Reproductive System
-Hermaphrodites
• -sexual reproduction
• - trochophore larvae
Trochophore larvapaddlelike, bristles
Apical tuft
Stomach
Ciliary band
Mouth
Anus
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Annelid development
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Class Polychaeta
• Many setae(bristles)
• Parapodia(paddlelike
appendages
• Marine
• Gonads only appear during
breeding season
• Predators of small animals,
prey for larger
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Class Polychaeta
Parapodium
Head
Tentacle
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Polychaete Worm
Predatory
Jaw
Tentacle
Palp
Everted pharynx
Eye
Cirrus
Parapodium
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Class Polychaeta
Fireworm
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Sedentary Polychaete Lugworm
http://arkive.org/lugworm/arenicola-marina/videos.html
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http://arkive.org/pompeii-worm/alvinella-pompejana-/video-00.html
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http://arkive.org/peacock-worm/sabellapavonina/
PEACOCK WORM VIDEO
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Class Oligochaeta
•
•
•
•
•
Few setae(bristles)
Clitellum
No parapodia
Hermaphroditic
Decomposers (aerate
soil)
• food for larger animal
Ex. Giant Gippsland
earthworm, earthworms
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External Structures of an Earthworm
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Lumbricus terrestris
• Feed on decaying
organic matter
• Enrich soil
• http://arkive.org/earth
worm/lumbricusterrestris/video-00.html
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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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Digestive structures:
o Crop: temporary storage sac
after mouth
o Gizzard: sac with muscular
walls to grind soil
o Intestine: stretches length of
body to aid in digestion of soil
o Anus: wastes are removed
Earthworms
Anus
Setae
gizzard
Clittelum
Other structures:
• Setae: bristles used for
movement (ventral side)
• Clittelum: enlarged segment;
secretes mucus & contains
reproductive parts
crop
Mouth
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Earthworm Reproduction-sexual
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Folds in an organ
inc. surface area
for the organ’s
function
Class Hirudinea
• Anterior & posterior
sucker-ectoparasite
• No setae
• hermaphrodites
• Most live in fresh water
• Dorsoventrally
compressed(flat)
• Ex. leeches
• Feed
– Invertebrates
– Body fluids
– Blood
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Leeches
o
o
o
o
o
o
o
Parasitic segmented worm
Most live in fresh water
Have no bristles for movement
move with muscular
contractions
Suckers used for attachment
to host
Some have suckers on tail also
http://arkive.org/medicinalleech/hirudomedicinalis/video-00.html
o Secrete anesthetic during bite
and release anticoagulant into
blood during feeding (to keep
blood flowing)
o Leeches were used in medical
procedures years ago to “bleed”
the sick
o remove “bad blood”
o now they are used in cosmetic
surgery, digit and limb
reattachment, and blood removal
from bruises