WORMS
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•Soft, Flattened, Acoelomates
•Keeps body cells in direct contact with
O2
•Bilaterally symmetrical
•Cephalized
•Have true tissues and organs
•Two way gut
•Have tissues and
internal organs
•Have all 3 germ
layers.
•Gas exchange
occurs by diffusion
through skin
Pharynx - muscular tube that extends through
the mouth and through which food is ingested
Planarians have flame cells to regulate body fluid
volume and composition
•Body fluids are filtered across the
flame cells.
•Waste is excreted through pores to
the outside.
Simple nervous system:
a. Paired ganglia form a brain.
b. Sensory cells are in the body wall.
Reproduction
Sexual and asexual reproduction
Asexual:
•Through regeneration
-Able to regenerate any lost parts
Sexual:
•Hermaphrodites
•Both worms exchange sperm
Planaria
Fertilized
eggs are
enclosed
in a
cocoon
and hatch
in two to
three
weeks
into tiny
worms
Classes
1-Turbellaria
•Planaria and relatives
•Free living, marine and
freshwater
•Two light-sensitive eyespots
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2- Tremotoda
• Flukes-blood, liver, lung
• Head ends has suckers or hooks
• Have reduced digestive, nervous, and excretory
systems.
• Reproductive systems are well developed and usually
hermaphroditic
• Parasitic- infecting the intestines of their host
• Covered by teguments that protect them from host
digestive juices.
– Examples:
• Schistosoma mansoni- blood fluke
• Burrow through skin, lay eggs in intestines
and past out of body
• Cause tissue decay
3-Cestoda
Tapeworms
•Absorbs nutrients through body
•
Taenia echinococcus
-Can grow to 30 ft long
-Has hooklets (Scolex)
for attachment
•No digestive system
•Absorb nutrients directly
through skin
•Proglottids
-Segments of the worm
Each proglottid
segment contains a full
set of both male and
female sex organs
Humans can be
infected by
eating beef that
has not been
cooked well
The tapeworm
attaches to the
lining of the
host with
suckers and
hooks
•A tapeworm scolex
contains hooks and
suckers for attachment
to intestinal wall of host.
• Behind the head is a
short neck and then a long
string of proglottids.
Life cycle of
Tapeworm
Tapeworm
releases
packets of
eggs which
exits with
the host
feces.
Some eggs
end upon
grass on in
field
Cow eats grassEggs hatch and burrow into cow’s
muscles, where they can become dormant
The blood
fluke
Schistosoma
infects
200 million
people,
leading to
body pains,
anemia, and
dysentery.
•Roundworms (nematodes),
hookworms
•Free-living and parasitic
•Aquatic and terrestrial
•Shaped like thick threads and
tapered on both ends
Body
•Unsegmented, bilateral symmetry
•Pseudocoelom
•One way gut
•Exchange gases through body wallsthrough diffusion
Reproduction:
-Most species have
separate sexes
-Internal fertilization
trichina worm: Trichinosis
Diseases
Trichinosis
--Humans, Pigs
-In humans, can be contracted by eating infected pork.
-Symptoms include abdominal pain, nausea, puffy and swollen face,
headache and vomiting. Can have permanent damage to the heart
muscles.
-Recovery in about 6 months
-5% of cases are fatal
Trichinella spiralis
• Trichinosis
After maturation, female adult
burrows into wall of small intestine
and produces living offspring that are
carried by bloodstream to skeletal
muscles where they encyst.
Muscle Biopsy Showing
Trichinosis
Ascarid Worm:
•Matures in the
intestines of the
host
•Eating
vegetables that
are not washed
Hookworms:
•Soil
•Walking barefoot
•anemia, malnutrition, and in
children causes under-development
Filarial Worm
•Tropical
regions
•Lives in
blood and
•Endemic in central Africa, Turkey, India,
lymph vessels
Southeast Asia, Australia, Philippines, and
of birds and
South America
mammals
•transmitted by mosquitoes
•After infection, the adult filarial worms migrate •Usually
to and live in the lymphatic ducts of
causes
humans. There, they clog up the blood
elephantiasis
vessels and cause the enlargement of the
various body parts. The worms then infiltrate
connective tissue.
Guinea worms
•Contaminated water containing infected water fleas
•Once in the human intestine, larvae burrow into surrounding tissue.
• The worms mate.
– Males die soon after, but pregnant
females continue to grow.
– As adults, each threadlike worm can be
three feet long and harbor three million
embryos. More than one guinea worm can
infect a person at the same time.
• About eight months later, the female
prepares to expel mature embryos by
migrating toward the skin surface.
• Extreme pain occurs as the worm
emerges from under the skin, often
around the infected person's ankle.
• The pain is temporarily relieved by
immersing the area in water, an act that
contaminates the water and starts the
cycle again.
•Ranging in length from less than
1 mm to 3 m for the giant
Australian earthworm.
•Annelids live in the sea, most
freshwater habitats, and damp
soil.
Diffusion of O2 and CO2 through moist skin
•Segmentation allows a high degree
of specialization of body regions.
–Groups of segments are modified for
different functions.
Segmented, Coelomates, Bilateral symmetry
One way gut
Ex: Earthworms,
leeches
Movement:
-By alternating the two
groups of muscles
1- Longitudinal
shorter or fatter
2- Circular
longer or thinner
-Setae: bristles
animation
Feeding and Digestion:
-Feed by sucking in soil and decaying matter
-Earthworms move food through the
pharynx-esophagus-crop-gizzard-intestines
•A muscular pharynx draws
food into the mouth.
•Food is stored in a crop
and ground up in a
muscular gizzard.
•Gizzard can contain sand
to aid in breakdown.
Chem
Mech
Absorption- Large folds in
the upper surface of the
intestine –typhlosole
(increases surface area)
Intestine
Gizzard & Crop
Pharynx
• Closed
circulatory
system
• Heart
consist of
five pairs
of aortic
arches
• Blood
contains
hemoglobin
Hearts
Nephridia (in each segment) for
excretion of nitrogenous wastes, urea.
•Wastes are discharged through exterior pores
Metanephridia of an earthworm
• Excretory system involves nephridia.
– a. Coiled nephridia tubules in each
segment have two openings: one is a
ciliated funnel that collects coelomic
fluid, and the other is an exit through
body wall.
– b. Between the two openings, a coiled
nephridia tubule removes waste from
blood vessels.
•Reproduction:
•Sexually
•Some have separate sexes and some
are hermaphrodites (earthworms and
Leeches)
•Earthworm: Clitellum secretes slim that contain eggs and sperm- the ring then
becomes a cocoon- young worms hatch a week later.
The received sperm are
stored while a special
organ, the Clitellum,
secretes a mucous cocoon.
• Nervous system has a brain
connected to a ventral solid
nerve cord; a ganglion is in each
segment.
• Long ventral nerve cord leads
from brain to ganglionic
swellings and lateral nerves in
each segment
nerve cord on the body
cavity's ventral surface
Classes of Annelida:
1- Oilgochaeta•Stream-lined bodies, few setae
•Earthworms, Tubifex Worms
Were used to treat
medical conditions
-Keep blood from
coagulating by hirudin, an
anticoagulant in their
saliva
2. Hirudinea
Leeches
Moist-tropical Climates
•most are parasites
use suckers to attach to
host and blade-like teeth to
make cut in host’s skin.
once used by doctors for
bloodletting
hermaphroditic
aquatic and terrestrial
3. Polychaeta (marine worms )
Sandworms, Blood Worms
•Live in Cracks and Creases in coral reefs, sand, mud, piles of rocks.
• Parapodia are paddle-like appendages used in swimming and for
respiration.
Ecology:
•Recycling in nature
•Diet of many birds
•Diet of fish
Coelom
The evolutionary significance of the coelom
cannot be overemphasized.
– The coelom provides a hydrostatic skeleton that
allows new and diverse modes of locomotion.
– It also provides body space for storage and for
complex organ development.
– The coelom cushions internal structures and
separates the action of the body wall muscles from
those of the internal organs, such as the digestive
muscles.
Name of
Disease
Causative
Organism
Vector
Definitive test
Human
Ascaroid
Ascaris
lumbricoides
Drinking infected
(sewage) water
Stool sample
Hookworm
Necator
americanus
Walk barefoot on soil w/
juvenile
Fecal Sample
Trichinosis
Trichinella
spiralis
Eating pig meat
w/encysted
Tissue Sample of
Muscles look for
encysted T. Spiralis
Elephantiasis
Wucheria
bancrofti
Mosquito Bite
Blood Sample look
for microfilaria
Guinea Worm
Dracunculus
medianansis
drink water/ swallow
cyclops
blood test, look for
microfilaria
River
Blindness
Oncocerca
volulus
Black Flies
"
Eye Worm
Loa loa
Deer fly
"
Dog
Heartworm
Dirofilaria
immitus
Mosquito, mostly Aedes
T. Spiralis
culex
"