Download I Annelida PPT

Phylum: Annelida - segmented worms
Class: Oligochaeta
Class: Polychaeta
Class: Hirudinea
Oligochaeta
Class: Polychaeta
Bristle worm
is poisonous and attacks sea anemones
Class: Hirudinea
Christmas tree worm
Class: Polycheata
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Yikes!!
Characteristics of
Phylum :Annelida—Little rings
 True
coelom
Each compartment is surrounded
by peritoneum which forms dorsal
and ventral mesenteries that
covers all the organs
 Hydrostatic skeleton
 Closed circulatory system
True coelom
*Centralized Nervous System*
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Brain
Double ventral nerve cord
Pair of ganglia in each segment
Lateral nerves
*Centralized Nervous System*
Sensory organs
 Taste
buds
 Statocysts - balance sensory
receptor
 Photoreceptor eyes with lenses
in some
Circulatory System
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Blood flows entirely in
closed vessels
Some spp. have hearts
Blood contains
hemoglobin, which
increases oxygen
carrying ability
Phylum Annelida
Excretory system
 Pair
of nephridia in each segment
Respiration
By gas exchange through
 Skin
 Gills
 Parapodia - fleshy paired
appendages
Body plan
 Bilateral
 Metameric-repeating
segments
(metamerism allows for budding)
 Setae-small hairs or sometimes
parapodia, i.e. small appendages
Body plan

Setae (“bristles”) of chitin
–
–
–
“anchors” for earthworm
“paddles” for polychaete
Enlarged as jaws in leeches, some polychaetes
Reproduction

Sexes are usually separate with gonads occurring in
each segment
–
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Some species have gonad specific segments
Breeding is usually seasonal (spring or fall)
As gametes mature they fill the coelom and are
released by the nephridia
Fertilization can be internal or external
Trochophore larvae develop, which are remarkably
similar to the Molluscs
Skin

Contains glands to secrete mucous and setae
Nutrition
 Eat
any dead organic material
 Consume up to one half their body
weight every day
Nutrition
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Annelids range from carnivores, herbivores,
scavengers, deposit feeders, and filter feeders
With very few defenses, many remain in a
burrow or secreted tube
Carnivores can capture prey with strong jaws
and quickly drag it back to its burrow
–
Can use a muscular pharynx = eversible proboscis
Digestion




mouth
esophagus
crop
intestines
gizzard
Mechanical –grinding in the gizzard
Chemical in the intestines
Extracellular and intracellular digestion
Environmental role
 Can
be found in fresh water, salt
water, soil
 Helps aerate/renutrify gardens
 Medicinal purposes
Classes
How do we classify
these segmented
worms into different
classes?
Class: Polychaeta
(many setae or hairs)
 20+
setae per segment
 Well differentiated head
 Specialized sense organs
 Parapodia
 No clitellum
 Mostly marine predators, e.g.
“Barry” the seaworm
Class: Polychaeta
(many setae or hairs)
Class: Oligochaeta
(Few long hairs)
 Clitellum
 Few
long, short or straight
setae; 2-4 clusters per
segment
 Land or marine, some
parasites
Class: Oligochaeta
(Few long hairs)
Class: Hirudinea
 Flattened
dorsalventrally
 Mostly freshwater, some marine
 Fluid feeder (blood)
 Clitellum
 Setae have developed suckers
 Specialized proboscis
Class: Hirudinea

Class Hirudinea
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–
–
–
pair of bladelike “jaws”
posterior “suction cup”
Predators
External parasites,
“bloodsuckers”
 Secrete anticoagulants
 Medicinal use
Blood Sucker

The salivary glands excrete hirudin which prevents the blood from
coagulating
–

Blood is broken down by symbiotic bacteria that is then used by
the leeches

Leeches were commonly used in the 19th century for bloodletting
–
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May also secrete an anaesthetic and substance to dilate small blood
vessels
Recent medical uses are to relieve pressure after vascular tissue is
damaged
– Snake bites or the reattachment of a finger or ear
Phylum Annelida