Segmented Worms
Diversity
 Live in all parts of the world (except Arctic and
antarctic regions)
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Can be marine, freshwater, or terrestrial
 Approximately 9,000 species
 Range in size from 1mm- 11 Feet
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Common Earthworm is 9-10 inches
 Known as segmented worms
 Ex: leech, earthworm
Characteristics of All Annelids
 Body System: Tube within a tube
 Inner tube is the straight line digestive tract
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Extends from mouth (first segment) to anus (last
segment)
 Outer tube consists of two layers of muscle, moist
skin, a cuticle, and secretion of slimy mucous
 Fluid filled cavity between the two tubes
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Contains a well developed circulatory system
Nervous system
Thread like kidneys
Reproductive organs
Characteristics of All Annelids
 Bilateral Symmetry
 Metamerism (segmentation)
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Increases the efficiency of body movement
Allows for greater complexity of the body
systems
 Muscular Structure
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Both longitudinal and circular muscles
Surrounded by moist cuticle (outer covering)
which aids in breathing
Characteristics of All Annelids
 Setae
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Used for locomotion
Leeches do not have these
 Coelom is well developed
 Circulatory system is closed
 Digestive System is complete
 Respiratory System

Gas exchange occurs through skin, gills, or
parapodia
Characteristics of All Annelids
 Excretory system
 A pair of nephridia
 Nervous System
 Double ventral nerve cord and pair of ganglia
 Sensory System
 Taste buds, photoreceptor cells and eyed with
lenses (in most)
 Reproductive System
 Hermaphroditic or separate sexes
 May have asexual reproduction
Classification
 Kingdom Animalia
 Phylum Annelida
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Class Oligochaeta
 Examples: Earthworms
Class Polychaeta – means many bristles
 Examples: lugworms, clam worms, bristleworms
 Approximately 8,000 species
Class Hirudinea
 Examples: leeches
 Often used in medicine to relieve swollen limbs, dry
skin, etc.
Worm composting
 Recycling the organic waste of a household into compost
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allows us to return badly needed organic matter to the
soil
Worm composting is a method for recycling food waste
into a rich, dark, earth-smelling soil conditioner.
Worm compost is made in a container filled with
moistened bedding and redworms
Add your food waste for a period of time, and the worms
and micro-organisms will eventually convert the entire
contents into rich compost.
Composting DIY
Class Oligochaeta
Earthworms:
•Burrow in soil
•Come out at night to explore
•Can drown if soil gets too wet
•Diet: scavengers (eat dead,
decaying matter)
•Have the ability to learn!
Class Polychaeta
Polychaetes:
•Ex: Christmas tree worm,
Fireworm, Scaleworm
•Largest group of annelids
•Mostly marine
•Brightly colored or can
be dull in color
Class Hirudinea
Leeches:
•Live mostly in freshwater
•More abundant in
tropical areas
•Most are carnivorous
(feed on meat, blood)
•Have two brains!
Characteristics of Earthworm (most
“famous” of Annelids)
 Soil is natural habitat
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Burrows head first into soil (makes its burrow by using
the pointed head end to push soil aside)
Eats soil for food (obtains nutrients/water from the
soil)
 Can feed on grass, leaf/scraps of organic matter
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Also digest humus (dead, decaying matter)
 Head end is light-sensitive
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Nocturnal—feed/eat/active during nighttime
Characteristics of Earthworm (most
“famous” of Annelids)
 Long, slender body (cylindrical)
 150-200 ring-like segments
 Locomotion/movement—performed by layers of
muscle in the body wall (circular bands of muscle)
 Ventral (belly) side has setae (bristle-like hairs) used
for movement
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Mature worms have a clitellum (produces the egg capsule
at breeding time)—larger segment (lighter in color)
Respiration—through its moist skin (cannot become
dry—worm would suffocate)
Characteristics of Earthworm (most
“famous” of Annelids)
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Organs:
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Pharynx—sucks in food (think of a vacuum)
Esophagus—food enters here once enters mouth
Crop—temporary storage (from esophagus)
Gizzard—grinds food into small pieces
Intestines—digestion and absorption occur here
Aortic arches—-part of closed circulatory system,
contains 5 of these, maintains a steady pressure of
blood to vessels
Ganglia—nervous system organ, brain
Characteristics of Earthworm (most
“famous” of Annelids)
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Nerve cord—runs from ganglia to each segment,
provides nerves to body structures
Blood vessel—part of closed circulatory system, moves
oxygen throughout body
Clitellum—reproductive organ, secretes mucus, stores
eggs/sperm during reproduction
Setae—movement and reproductive purposes
Segments—mouth-anus sensory/excretory organs are
attached to muscle wall of each segment
Anus--excretion
Nephridium—excretory organ, excrete ammonia
Earthworm Dissection
YouTube Earthworm Dissection
Characteristics of Earthworm (most
“famous” of Annelids)
 Other/Biosphere/Uses
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Help to aerate the soil
Prepare soil with nutrients from excretory waste
products
Leeches can be used for medicinal purposes (for
blood clotting issues)
Earthworms: eat, fishing, aerate soil, etc
Earthworm Pictures!
Earthworm Pictures!