Transcript Phylum Annelida (Segmented Worms)

Phylum Annelida
(segmented worms)
I. Main Characteristics
• Bilateral Symmetry
• Segmented: Body is divided
into segments
Other Traits
- Annelida means “little rings”
- body segments separated by septum
= internal wall
Main Characteristics
true coelom (body cavity)
Characteristics Cont.
• Protostomes
–Blastopore develops into mouth
• Triploblastic
–3 embryonic layers
–Ectoderm, Mesoderm, Endoderm
II. Characteristics Cont’d
Setae-short hair-like bristles
that function in locomotion
have well-developed
nervous system (brain)
Ganglia and ventral nerve cord
-have closed circulatory system
Characteristics Cont.
• Excretory System
–Nephridia
•Filters and collects
nitrogenous waste and
empties them from the body
- sexual reproduction in annelids
- some are hermaphrodites
3 Main Annelida Classes
1.Class Polychaeta
2.Class Oligochaeta
3.Class Hirudinea
Annelids
Include:
earthworms
marine worms
leeches
This is a scale worm (Polychaetes).
They live 1000 meters below the
water’s surface and can turn their
mouths inside out.
III. Annelid Classes
• Class Polychaeta (marine
worms)
Interesting facts!
• Polychaetes are the largest class of
annelid worms
–5300 species!
• Most are between 5 to 10 cm long
Class Polychaeta
Marine worms
-includes:
sandworms,
bloodworms,
fireworms
-have paddle-like
appendages with
setae
IV. Class Polychaeta
bottom-dwellers
Parapodia-lateral extensions of the body
Cuticle- protective non-living layer
V. Segments
• 1st SegmentProstomium
–Contains eyes,
antennae, etc.
• 2nd SegmentPeristomium
–Surrounds mouth and
bears sensory
tentacles
VI. Polychaete Feeding
• Most carnivorous
–Gut is straight tube
–Extract nutrition from sediment
–Gut has a crop &
gizzard
• Some can get food by
diffusion
VII. Other Polychaete Systems
Respiration by diffusion
Chemoreceptors (help seek out food)
Statocysts (detect gravity; if the
worm is upside down or not)
Nephridia for excretion
VIII. Polychaete Reproduction
• Mostly separate sexes
• Both Asexual and Sexual Reproduction
• Asexual reproduction
–Budding and Fission
• Sexual Reproduction
–Most fertilization is external
• Can have alternation of generations
Nereis
Featherduster
Fireworm
• Class Oligochaeta
(Earthworms)
Class Oligochaeta – Earthworm
-Few setae
-Live in soil or fresh water
-Castings - enrich soil, (worm poop)
Interesting facts!
Earthworms may survive
being frozen if the freeze is
not too rapid
 Have been kept alive for 6
years, but in the wild
probably live two years at the
most.
IX. Class Oligochaeta
• 3000 Species
• Mostly freshwater or
terrestrial
• Clitellum
–Used for mucous secretion
during copulation and
cocoon for mating
• Setae: short bristlelike hairs on the
outside of the
worm’s body.
–Function in
anchoring and
movement
Section 27-3
Earthworm Anatomy
Anus
Setae
Body segments
Gizzard
Crop
Dorsal
blood vessel
Clitellum
Mouth
Brain
Ganglion
Circular muscle
Longitudinal
muscle
Nephridia
Ganglia
Ring
vessels
Reproductive
organs
Ventral
blood vessel
X. Oligochaete Feeding
• Complete digestive tract
• Path of Food
–Mouth pharynx esophagus crop
gizzard stomach intestine
Oligochaete Feeding
• Eat practically everything they come
across (anything that will fit into their
pharynx)
• Sucks a mixture of detrius and soil into its
mouth – digests what it can and the rest
exits the body through the anus
(castings)
XI. Other Oligochaete Systems
Respiration through moist
skin
Circulatory System
• A “closed system”
–2 main blood vessels
• Dorsal Longitudinal Vessel
• Ventral blood vessel
• 5 aortic arches
with 10 hearts
Nervous System
• Primitive with cerebral ganglion (brains)
• Nerve cords - run the length of the body.
Excretory System
• Nephridia- primitive kidneys
–Filter and get rid of nitrogenous wastes
–Excrete ammonia and urea through
nephridiopores
Excretory System
XII. Oligochaete Reproduction
• Hermaphrodites
–Sperm transfer between two individuals
• Two worms line up anterior to posterior
ends
• Copulation lasts between 2-3 hours
Reproduction Cont.
• Cocoon formed
–Fertilization occurs here
–Clitellum
• Some freshwater species
asexual
Oligochaete Reproduction
Class Hirudinea (Leeches)
Class Hirudinea
-Leeches
-external parasites with suckers on each end
-medicinal uses
(circulation,
anti-clotting)
Leeches being bred for medical uses.
What would you do to cure a swollen foot?
XII. Class Hirudinea
• Mostly external parasites
• No parapodia
• Secondary annuli on segments
• Circular, longitudinal, and
oblique muscle layers
XIV. Hirudinean Feeding
 Two main sources of food:
-small invertebrates (snails, etc)
-body fluids (blood)
Mouth in the anterior sucker
Produce “hirudin”- anticoagulent
(stops blood from clotting)
XV. Other Hirudinean Systems
• Gas exchange by diffusion
• Sensory Receptors:
–Photoreceptors
–Can sense temp.
XVI. Hirudinean Reproduction
•
•
•
•
All monoecious
All sexually reproducing
Clitellum seen during breeding season
No larval stages
Recap: Taxonomy
Kingdom Animalia
Phylum Annelida
Class Oligochaeta (earthworms)
Class Hirudinea (leeches)
Class Polychaeta (marine worms)
*All are segmented, and have a coelom