6. Bilateral symmetry- with external and internal
features arranged symmetrically on either side
of a median or sagital plane
Bilateral symmetry: active mode; Biradial symmetry: sedentary life
ADVANCEMENTS:
Nervous system
Anteriorbrain
Paired ventral nerve cords
Longitudinal
Incomplete gut (Digestive system)
No anus
Food exits via mouth
7. Excretory system & osmoregulation
Diffusion
across body wall
Protonephridia
Specializedexcretory organs
May also help osmoregulate
Formed reproductive organ
10. Class Turbellaria
Free living
Freshwater
Planarians
such as
Dugesia
A few inhabit
terrestrial
(moist) habitats
11. STRUCTURE
Dugesia is a thin, slender, soft worm about
15mm long, bluntly triangular anterior end,
or “head,” and a tapered body patterned
with dark pigment.
Head region bears two black eyespots
middorsally
The mouth is on ventral surface near the
middle of the body
12. Through it a tubular pharynx, or
proboscis, with muscular walls can be
extended to capture food.
Excretory openings, present laterally on
the dorsal surface but are difficult to see.
Genital pore, mature worm has it on the
ventral surface behind the mouth.
Body covered by epidermis of single layer
of cuboidal to columnar cells.
15. The epidermal cells contain small bodies
called rhabdites, and many deep-lying
unicellular glands that open the surface.
Gland cells produce mucus.
Ventral epidermis is covered with cilia for
locomotion
Beneath the basement membrane are the
layers of muscle fibers, circular,
longitudinal, and diagonal, also
dorsoventral fibers.
16.
17. Spaces between the muscles and internal
organs are filled with parenchyma
(mesenchyme)
There is no body cavity
In the parenchyma are scattered free
formative cells, which by mitosis produce
new parts in regeneration.
18. Class Turbellaria
Marine species (beautiful colors)
Significantmembers of coral reef
ecosystems
Some are major predators of colonial
ascidians (sea squirts)
Others are pests of commercial clams
and oysters
Some live symbiotically on a variety of reef
invertebrates
19.
20.
21.
22.
23.
24.
25. Class Turbellaria
Locomotion
Usually by cilia
Dugesia can move at about 1.5 mm/sec
Peristaltic waves can achieve higher
velocities
Marine flatworms can use this to swim
gracefully
26.
27. Class Turbellaria
Locomotion
Terrestrial planarians
Glide smoothly on the substrate by the action of
powerful, closely spaced cilia in a special medial
ventral strip (creeping sole), on a thin coat of
mucus secreted on the substrate by glands
opening into the creeping sole
Planarians that migrate on plants or objects above
the ground sometimes lower themselves to the
ground on a string of mucus.
30. Muscular System
Below the epidermis are layers of
circular and longitudinal
muscle fibers; used in
locomotion
31.
32.
33. Class Turbellaria
Feeding Ecology
Mostturbellarians are carnivorous predators or
scavengers.
Carnivores feed on organisms that they can fit into
their mouths, such as protozoans, copepods, small
worms, and minute mollusks.
Some species use mucus that may have poisonous
or narcotic chemicals to slow or entangle prey.
Some have specific diets and feed on sponges,
ectoprocts, barnacles, and tunicates.
Several species have commensal relationships with
various invertebrates
34. Feeding and Digestion
The pharynx is protruded from the mouth and
into the prey.
The pharynx and gut cells produce digestive
enzymes that breakdown food extracellularly.
Because these worm lack a circulatory system,
larger species have extensive anastomosing guts to
aid in distribution.
Since these worms have incomplete guts, all waste
must pass back out of the mouth.
37. Nutrition
Planaria store food in digestive epithelium and
can survive many weeks shrinking slowly in size
without feeding.
They are capable of utilizing their own tissues
such as reproductive tissue for food when
reserves are exhausted.
Lab animals often tend to shrink in size when not
fed properly
38.
39. Digestive system
Ventral mouth
Muscular pharynx
A blind intestine (details depend on order)
Tricladida — 10-20 mm long
Tripartite gut; one main anterior branch and two
main posterior branches with numerous blind
pockets off all three. Dugesia
Polycladida — up to 5 cm long
Gut has numerous branches ramifying
throughout the body.
41. Excretory System
Protonephridial System- comprises 2
longitudinal ducts connecting to a network
of tubules that branch throughout the body
and end in in many large flame cells.
Flame cells- they collect excess water or
fluid wastes
Osmoregulation-removing excess fluids
from the organism, although small
amounts of ammonia are also removed.
42. Class Turbellaria
Protonephridia
One end of the tubule opens through a small pore
to the exterior. The other end of the tube ends
blindly within the body in a spherical structure
containing long cilia - these are called flame cells
Excess water (and possibly wastes) enters the
flame cell system and is propelled through the
tubules toward the outside by the beating of the
cilia (the "flame").
43. Protonephridia
Branches terminate in blind flame cells.
Flame cells have slits that penetrate the cell
Slits are crossed by filaments or a membrane that
reduce the effective pore size
Slits act as an ultrafilter to keep back large proteins
Filtrate of mesenchymal intercellular fluid enters
tubule.
Inorganic and organic materials actively
reabsorbed in tubule; remainder is excreted
48. Nervous System
More organized
Two cerebral ganglia= “brain”
Short nerves extend to the anterior end
and the eyes, and two longitudinal nerve
cords pass back
With many transverse connectives and
peripheral nerves
49. Nervous system and sensory organs
Dorsal, anterior eyes
Ciliated pits behind auricles on head are
probably chemosensors
Dorsal, bilobed brain underlays eyes
Primitively 3-4 pairs of longitudinal nerve
cords
Reduced to two longitudinal ventral nerve cords
Run down length of body with numerous cross
connections and branches in most groups.
57. Reproductive System
and
Reproduction
Thereare two types of reproduction;
asexual reproduction
sexual reproduction
58. Asexual Reproduction
They reproduce asexually by transverse
fission (split into two) and have great
regenerative capabilities. This means that
if a part of their body is cut into half, they
are able to grow the lost body part within a
period of time.
59.
60.
61. Sexual Reproduction
Most Turbellarians are hermaphroditic,
meaning that they contain the male and
the female sex organs. However, they are
unable to self-fertilize and thus need the
sperm of other turbellarians to fertilize the
egg.
62. The MALE Reproductive System
Several hundred small spherical testes
along both sides of the body, each connected
by,
a minute ductus eferens to,
A larger ductus deferens: the 2 ducts enter
Median seminal vesicle for sperm storage,
connects to,
Muscular penis opening into.
Genital atrium, just within the genital pore
63. The FEMALE Reproductive System
2 rounded ovaries, connecting to,
Two oviducts
Along each duct are: many yolk or vitelline glands,
which supply yolk cells when eggs are produced
the 2 oviducts join the median vagina opening into,
The genital atrium, to the vagina is connected
A bulbous copulatory sac that receives sperm at
mating
Soon the sperm move to the seminal receptacles
which are slight enlargement between the ovaries
and oviducts.
64.
65.
66.
67. REPRODUCTION
Cross-fertilization- exchange of sex
products between separate individual
Internal fertilization- direct transfer
of sperm from male to female organ
Development is direct
68.
69.
70.
71. Ecology and Evolution
Many flatworms are brightly coloured
Warning coloration (aposomatic coloration)
These flatworms are believed to be toxic or
distasteful
Other species are mimics of toxic nudibranchs
(sea slugs)
72. Other Turbellaria
ACOELA
Have mouth but without digestive cavity
Lacks excretory organ
Have no distinct gonads
Nervous system is an epidermal net system
Free living and others live in the intestines of
sea urchins and sea cucumbers
74. Characteristics
All parasitic, mostly in vertebrates
Covered externally by a non-ciliated syncytium
(tegument)
Oral sucker surrounds mouth
Ventral sucker used for attachment
Mouth is anterior
Digestive tract is -shaped,, with 2 main trunks
and smaller branches
Complex life cycles (involving at least one
intermediate host)
75. The food consists of the tissues or body fluids
of the host, which are sucked in by action of
the muscular pharynx
Are more like turbellarians
Complex muscle layers, excretory organs,
and a nervous system
Parasitic life, the development of a resistant
cuticle, suckers, and hooks and general lack
of sense organs.
Sensory organs, such as dorsal eyespots
occur in some larve and in some flukes that
are ectoparasites.
76.
77. Subclass Monogenea
Inhabit only one host
Ectoparasites of fishes, amphibians, and
reptiles, but some inhabit the mouth
cavities or urinary bladders.
At the posterior end is a well-developed
adhesive organ with one or more suckers
and chitinous hooks or anchors
Cross-fertilization
Development is direct adult form
78. Subclass Aspidobothrea
Internal parasite of lower vertebrates
and mollusks and have but a single host
Characterized by huge adhesive
structure (sucker) covering the whole
ventral part of the body
They show features of both Monogenea
and Digenea and may have one or two
hosts.
79.
80.
81. Subclass Digenea
Largest group of trematodes
All internal parasites
Must live in two or more host species to
complete the life cycle, larvae in a certain
snail (intermediate host) and the adult in
some vertebrate (primary host)
Live in the parts of digestive tract, lungs,
urinary bladder, blood vessels, or other
organs
82. Sheep liver fluke
Common liver fluke or Fasciola hepatica
Inhabits the bile ducts and sometimes
invades other organs
Commonest in sheep and cattle but is
sometimes found in other mammals and
occasionally in humans, producing the
disease known as liver rot or fasciolosis
83. One of the largest flukes of the world,
reaching a length of 30mm and a width of
13mm
It is leaf shaped, pointed posteriorly and wide
interiorly
The anterior sucker is terminal surrounding
the mouth, and close behind is the ventral
(posterior) sucker for attachment in host
Between them the genital opening
Digestive system: mouth, muscular pharynx,
short esophagus, and two branched enteron.
84. Muscles are complex
Excretory has many flame cells
Nervous system: double ganglion,
2 lengthwise nerve cords, and
various nerves
Hermaphroditic
85. The testes are large and greatly
branched, arranged in tandem behind the
ovary.
The smaller, dendritic ovary lies on the
right side, coiling between the ovary and
the preacetabular cirrus pouch. Vitelline
follicles are extensive, filling most of the
lateral body and becoming confluent
behind the testes.
86. Fasciola hepatica
Commonly known as the sheep liver fluke
Important parasite of sheep and cattle
(other grazers) can be found in humans.
Morphology
Large size, frequently over 30 mm long
Characteristic cone-shaped projection at
anterior end followed by wide shoulders
88. Fasciola hepatica: Trematode
Life Cycle Representative
Ova or egg
Miracidium
Sporocyst
(Daughter sporocyst, or redia)
Cercaria
Metacercaria
Adult
89. Stages of Trematode Life Cycle
Ova or egg - shelled embryo.
Contains miracidium inside shell
Under appropriate conditions, the operculum
(cap on shell) opens to allow miracidium to
escape.
Many of flukes have very distinctive eggs.
90. Stages of Trematode Life Cycle
Miracidium
Ciliated organism that can be mistaken for a
ciliated protozoan.
In species that hatch in water, it contains
penetration glands that release histolytic or
proteolytic enzymes to help penetrate snail
Some species do not hatch until eaten by
snail host.
91. Stages of Trematode Life Cycle
Sporocyst
The miracidium develops into sporocyst often
in the digestive gland of the snail.
The sporocyst is an embryonic bag or
germinal sac.
The sporocyst will produce many daughter
stages called rediae or in some cases
daughter sporocysts.
92. Stages of Trematode Life Cycle
Rediae or Daughter Sporocyst
Infunction they are very similar to sporocysts.
Contain digestive tract and are more active
Asexually reproduce to yield many cercariae.
Some species they can live for many years.
93. Stages of Trematode Life Cycle
Cercariae
Usually escape snail and often swim by some
means of tail structure.
Responsible for transmission from snail to the
next host.
94. Stages of Trematode Life Cycle
Metacercaria
Resistant stage that is formed in many
species
Cercaria that have this stage contain
cystogenic glands that helps the organism
encyst on vegetation.
Cercaria that form metacercaria in second
intermediate hosts, often have penetration
glands that enable them to penetrate the
second intermediate host.
95. Stages of Trematode Life Cycle
Adult
Always found in the definitive host
Responsible for sexual reproduction
Often restricted to specific region of host.
Often very host specific.
99. Fasciola hepatica
Adult in bile duct of definitive host passes
eggs in feces.
If eggs land in water, they hatch into
miracidium that actively swims until it finds
an appropriate snail. (Galba truncatula)
Penetrates snail, develops into germinal
sac (sporocyst), asexual stages of rediae
and cercariae formed.
100. Fasciola hepatica
Cercariae leave snail, encyst on
vegetation, and form metacercaria.
Herbivore infected when it ingests
vegetation with metacercaria.
Metacercaria develop into adult
penetrates gut wall, moves to the liver.
Humans infected by eating watercress that
has metacercaria on it.
101. Schistosoma sp.
Adult worms are found in blood vessels of
digestive tract or urinary bladder thus
called blood flukes
male worm has a split body called the
gynecophoral canal. The female is
usually found within this canal “safe in the
arms of her lover.” She leaves only during
the egg laying period.
102.
103.
104.
105. Schistosomiasis
Migratory phase - 4-10 weeks after
infection. Is characterized by fever and
toxic or allergic reactions resulting from
migration of immature organisms. Often
results in bronchitis, hepatomegaly,
splenomegaly, and diarrhea.
106. Schistosomiasis
Acute phase - 10 weeks to years. Eggs
can become trapped and produce
granulomas and scar tissue.
Form fibrous nodules called pseudotubules.
Eggs may lodge in gastrointestinal, renal,
neural, and other systems.
A person infected with 50 mating pairs would be
exposed to about 15,000 eggs per day for several
years. ½ of eggs might remain trapped in tissues.
107. Schistosomiasis
Chronic phase - persons living in endemic
regions are often asymptotic. May have
mild, chronic bloody stools or urine. Often
have formation of granulomas.
Hepatomegaly, Spleenomegaly, Ascites
(accumulation of fluid in abdominal cavity
fig 16.17, page 245.
108. Epidemiology
Human waste into water.
Moslem religious practice of ablution
Agricultural projects
Irrigation extends snail habitats
Use of night soil (human feces)
Planting and harvesting of water crops
Dependence of people on rivers.
109. Epidemiology
Before the Aswan Dam was built, the
region between Cairo and Aswan was
subject to annual floods. The prevalence
of Schistosomiasis was only about 5%.
Four
years after completion of the dam the
prevalence ranged from 19%-75%
(average 35%) or a 7 fold increase.
110. Schistosoma sp.
Important parasites of man and some
domesticated animals
Three species infect man
Schistosoma mansoni
Schistosoma japonicum
Schistosoma haematobium
similar see table 16.1 pg 237 for
differences
111. Schistosoma japonicum.
Common in parts of Japan, China,
Taiwan, Philippines, Thailand, and other
parts of Southeast Asia.
Most pathogenic and most difficult to
control
Located in blood vessels of small
intestine.
Eggs may lodge in brain causing CNS
damage, coma, and paralysis.
112. Schistosoma mansoni
Common in Egypt, the Middle East, parts
of Africa, and parts of South and Central
America.
Found in portal veins draining large
intestine
The sharp lateral spine is distinctive
Primary pathological effects come from
the damage done by eggs.
113. Schistosoma mansoni
In heavy infections eggs become trapped
in the mucous and submucosa of the gut
and cause granuloma formation
If extensive, they can cause colon
blockage and significant blood loss.
In liver can cause hepatomegaly.
Destruction of lungs and heart tissue.
Reservoir hosts are of limited or no
importance
114. Schistosoma haematobium
often referred to as Bilharzia after
Theodore Bilharz who discovered it.
found in parts of Africa, and parts of the
Middle East, southern Europe and some
parts of Asia.
Found primarily in the veins of the urinary
bladder. Eggs released in urine.
They are least pathogenic
115. Diagnosis, Treatment, and
Control
Finding eggs in feces or urine
Biopsy - in chronic cases if eggs not
passed
Treatment - very difficult - page 245-246.
Control is very difficult
Customs and traditions
Agricultural practices
Socioeconomics
116. Schistosome cercarial
dermatitis or swimmers itch
Schistosomes of animals other than man
(usually rodents and birds) try to penetrate
the skin of man, they can not establish
themselves in the blood vascular system
of man.
Often cause a dermatitis which can be
severe and in some cases life threatening.
Allergic reaction
118. Fasciolopsis buski -
Intestinal fluke of man
large fluke infects man when he ingests
metacercaria found on vegetation
including water chestnuts, bamboo, and
water caltrop.
eat these raw or peel or crack with teeth.
elimination of feces (human and animal)
into water and use of night soil for farming
119.
120. Fasciolopsis buski -
Pathology
Blockage of food passage or interference with
normal digestive processes
Destruction of intestinal tissue resulting in
ulcers, hemorrhages, and abscesses
formation
Chronic diarrhea
Verminous intoxication - result of absorption
of parasite metabolites (waste products), can
lead to death.
121. Dicrocoelium dendriticum
Common parasite of herbivores, rare in
man
Not dependent upon aquatic environment
Eggs eaten by land snail (asexual
reproduction occurs producing cercariae.
Cercariae surrounded forming slime balls.
Ant eats slime ball and metacercaria
develop.
Herbivore infected by ingesting ant.
124. Dicrocoelium dendriticum
Modification of host behavior
Causes ant to climb to tips of grasses
early morning and late evenings.
Increases odds of ant being eaten.
125. Paragonimus westermani
the human lung fluke, it is found in the
Orient including India and Philippines
Definitive host becomes infected by eating
improperly cooked crustacean. Adult
infections become established in lungs but
larval forms may wander into brain, pleura,
mesentery, etc.(ectopic infection).
127. Paragonimus westermani
Reservoir hosts include - dogs, cats, pigs,
rodents, and other animals
Man becomes infected by eating
improperly cooked crabs, ingestion of
metacercaria from cutting boards where
salads are fixed, medicinal use of crab
juices)
Smoked or pickled crab do not kill
128. Paragonimus westermani
Pathology
Early invasive stages usually asymptomatic.
In the lung or ectopic site, connective tissue
forms pseudotubertules. In the CNS, they can
cause paralysis and in rare cases can be fatal.
In the heart they can cause severe damage and
can be fatal.
Lung infections cause chronic cough, bloody
sputum, pneumonia -like conditions.
129. Paragonimus westermani
Prevention includes
Cooking of crabs, crayfish
Care when eating salads, no crab juice.
Proper disposal of feces and sputum.
130. Clonorchis sinensis
(Opistochonorchis sinensis)
Commonly called the Chinese liver fluke,
Asian liver fluke, Oriental liver fluke, and
Human liver fluke
Common in Orient including Japan, China,
Korea, Taiwan, Viet Nam.
Many immigrants from Orient living in the
United States are infected.
131. Clonorchis sinensis
Man becomes infected by eating
improperly cooked fish containing
metacercaria.
Metacercaria may contaminate other
foods such as salads, etc.
Smoking, drying, pickling fish often fails to
kill the metacercaria.
135. Characteristics
Mostly slender and elongate
With flat body usually of many short similar
sections
Complete lack of Digestive system
They lack cilia
Covered with tegument
Have complex muscle layers, parenchyma,
paired excretory ducts with flame cells, and
nerve ring with 3 pairs of nerve cords.
136. Food is absorbed directly through body
wall
All are endoparasites, the adult worms is
in the intestines of vertebrates and the
larvae in tissues of some alternate host.
Defining characteristics
Scolex
Proglottids
137. Subclass CESTODARIA
Small worms lacking a scolex
each with sucker for attachment
the body undivided
one set of reproductive organs
Similar in outward appearance to
trematodes
But the larva is like tapeworm and LACK
digestive tract.
138.
139. Subclass EUCESTODA
Have scolex
Ex: Taenia solium (pork tapeworm of humans)
SCOLEX “head” - a minute knoblike with four
muscular suckers or sucker disc on the side and
a circle of hooks on the elevated tip, or
rostellum.
A short “neck”, or budding zone, joins the scolex
to the body, or strobila, which consist s of a
series of up to 1000 proglottids.
148. The suckers and the hooks serve to fasten
the scolex to the intestinal wall of the host.
Scolex contain nerve ring
Each proglottid contains muscle,
parenchyma, sections of the excretory
canals connected by a cross canal, many
flame cells in the nerves
Complete set of both male and female sex
organs develops in every prolottids
149. Since individual prolottid has a
complete set of both male and
female sex organs…
DO YOU THINK IT IS POSSIBLE
FOR EVERY PROGLOTTID TO
FERTILIZE ANOTHER
PROGLOTTID????
151. Fact.
Self-fertilization between the systems in
one proglottid or in sepatarete proglottids
or cross-fertilization between parts in two
worms in one host are all possible.
152. Life cycle of the pork tapeworm.
Taenia solium
Feces
Oncosphere
Eggs eaten by pigs
Eggs encyst in intestine
Cysticercus- bladder worm
Hollow papilla projecting in the sac
In the cavity of papilla, scolex develop
Eaten imperfectly cooked pork
The papilla everts to form a scolex and neck
Scolex attaches to the host intestine
A new tapeworm begins to form
153.
154. Beef Tapeworm,
Taeniarhynchus saginatus
• Definitive host humans; intermediate host cattle
• Eggs are shed with human feces; infected persons defecate in a
pasture and the eggs are ingested by cattle
• Eggs hatch giving rise to oncosphere larvae that bore into the
intestinal wall and get into the circulatory system to be
transported to muscle
• Here the larvae develop into the cysticercus stage (=the
bladder worm) with the inverted scolex
• If uncooked beef is consumed the cysticercus is freed and the
scolex everts, forming the adult
• Symptoms include loss of weight, chronic indigestion, diarrhea
161. The free swimming coracidium is eaten
by 1st intermediate host usually an
aquatic arthropod!
Copepod
162. In the copepod the second larval stage
(PROCERCOID)
Frontal glands
Cercomer posterior end
163. 2nd IH is a vertebrate of some kind
(usually cold blooded)
164. The 3rd type of larva that develops in the
2nd IH is the PLEROCERCOID
The cercomere is lost and a scolex develops (no proglottids)!
165.
166.
167. Human Infections of Spirometra
(Diphyllobothrium) mansonoides
A few cases
in the US
have involved
finding
plerocercoids
in the eyes.
168. Sparganosis
Disease
Humans infected with
plerocercoid
Ingestcopepod
Eating raw meat with
plerocercoids
Plerocercoid transfers to
human
Frogor snake flesh
poultice
Pluerocercoid moves into
human tissue
169. Human Infections of Spirometra
(Diphyllobothrium) mansonoides
Parasite is rare - only about 40 cases of human
sparganosis have been reported in the U.S.
170. Sparganosis
Seriousness depends on
Where plerocercoid establishes
Number
If reproduction occurs
Removed by surgery
171. ADJUSTMENT TO PARASITIC
LIFE
1. The integument protects against digestion
by host alkaline digestive juices but is
freely permeable to water and nutrients.
o Nutrients—mostly amino acids and simple
sugars broken down from complex molecules
by the host
o Adults—resistant to alkaline pancreatic juice
172. 2. The internal osmotic pressure is lower
than that of the surrounding host fluid or
tissue.
3. The pH tolerance is high, 4 to 11.
4. The tissues have high glycogen content
(to 60% of dry weight) and much lipid but
far less protein.
Fatty acid are derived from anaerobic metabolism of
glycogen
Carbohydrates in the host diet induces growth ,
longevity , and production
173. 5. Oxygen is used in respiration if
available, but anaerobic
predominates.
6. Eggs eaten by the intermediate host
must experience both acid and alkali.
Hence are released only in the
intestine.
174. Adaptations of parasites in
general:
1. Sense organs are usually much reduced
or absent
2. Some mechanism of attachment to the
host tissue is developed (hooks, suckers)
3. There is increased egg production
coupled with a larval stage to facilitate
survival and infection of new host.
The dorsal epidermis contains numerous secretory vesicles and rod-shaped membrane enclosed secretions, the rhabdites (rhabd = rod). Rhabdites are synthesized by epidermal gland cells submerged below the basal lamina into the parenchyma. When expelled at the surface, rhabdites absorb water and expand to become sticky mucus which may help trap small invertebrate prey.
ANASTOMOSIS the union of parts or branches (as of streams, blood vessels, or leaf veins) so as to intercommunicate or interconnect
Dugesia is a genus of dugesiid triclad that contains some common representatives of the class Turbellaria . These common flatworms are found in freshwater habitats of Africa , Europe , Middle East , Asia and Australia . Dugesia is best known to non-specialists because of its regeneration capacities.
Three types of proglottids: immature, mature and gravid.