LESSON 4: PLATYHELMINTHES Flashcards
(137 cards)
1
Q
Platyhelminthes originate from Greek word?
A
Platys= Flat
Helmins= Worm
2
Q
4 classes of Platyhelminthes
A
- Class Turbellaria
- Class Trematoda
- Class Monogenea
- Class Cestoda
3
Q
Free-living flatworms occur exclusively in
A
class Turbellaria
4
Q
____________ and some others prefer frequent
streams and spring pools; others prefer the
flowing water of mountain streams.
A
Planarians
4
Q
Many, especially larger species, occur on the undersides of stones and other hard objects in ____________________________________________
A
freshwater streams or in littoral zones of
the ocean
4
Q
A few ____________ are symbiotic (commensals or parasites), but
most are adapted as bottom-dwellers in marine or fresh water or live
in moist places on land.
A
turbellarians
4
Q
are freshwater planarians
A
Dugesia
4
Q
Distinct morphological characteristics to differentiate parasitic classes to most turbellarians
A
Most Turbellarians: ciliated cellular epidermis
Parasitic Classes: non-ciliated body covering
5
Q
_____________ inhabit moist places
such as under stones and logs or on moist
vegetation.
A
Terrestrial turbellarians
6
Q
The non ciliated body covering of parasitic classes is called?
A
Syncytial tegument (syncytial= many nuclei in single cell membrane)
6
Q
Adults of Trematoda, Monogenea, and
Cestoda share a ____________
A
syncytial covering
7
Q
____________ unites these three parasitic classes based on this shared characteristic
A
Neodermata
7
Q
The tegument completely lacks ___
A
Cilia
7
Q
derived from mesoderm, fill spaces between muscles and internal organs
A
Parenchyma cells
7
Q
The syncytial covering is called the ______
A
Tegument
8
Q
This unique tegument is a defining feature of the taxon _________
A
Neodermata
8
Q
Below the basal lamina in flatworms, the body wall contains muscle layers:
A
*Circular
*Longitudinal
*Diagonal
9
Q
Parenchyma cells form a _______ structure
A
Meshwork
10
Q
In some (possibly all) flatworms, parenchyma cells are _______________ of muscle cells, not a distinct cell type
A
noncontractile portions
11
Q
In turbellarians the muscular
pharynx opens _________ just
inside the mouth, through
which it can extend
A
posteriorly
11
Q
The digestive system of most
Platyhelminthes includes a
A
mouth, pharynx, and intestine.
12
Q
The intestine may be _____________
A
simple or branched.
13
Q
The mouth is usually at the
anterior end in _________, and the
pharynx is not protrusible.
A
flukes
14
Q
Platyhelminthes: Intestinal secretions contain ____________ for some extracellular
digestion.
A
proteolytic enzymes
15
Platyhelminthes: Food is sucked into the intestine, where cells of the ___________ often
phagocytize it and complete intracellular digestion.
gastrodermis
16
Platyhelminthes: Undigested food is egested through the __________
pharynx
17
____________ lack a digestive system and must absorb all of their nutrients as small molecules (predigested by the host) directly through their
tegument.
Tapeworms
18
Except in some turbellarians, the
osmoregulatory system consists
of canals with tubules that end in
flame cells called___________
protonephridia
19
Each flame cell surrounds a small
space into which a ____________
projects.
tuft of flagella
20
The beat of the flagella in flame cells (resembling a flickering flame) provides a _______________ to draw fluid through the weir into the space (lumen) enclosed by the
tubule cell.
negative pressure
21
Platyhelminthes: The ______continues into ____________ that finally open to the outside by ________.
Lumen--->collecting ducts--->pores (opening)
21
The simplest system, found in some
turbellarians, is a______________________
resembling the nerve net of the cnidarians.
subepidermal nerve plexus
21
Platyhelminthes: The wall of the duct beyond the flame cell commonly bears folds or __________ that probably function in reabsorption of certain ions or molecules.
microvilli
21
Other flatworms have, in addition to a nerve
plexus,_________________________ lying under the muscle layer
one to five pairs of longitudinal nerve
cords
21
Flatworms are __________ but vary in the
complexity of their nervous system.
cephalized
22
It is likely that this system is osmoregulatory in most forms; it is reduced or
absent in ______________, which do not have to expel excess water
marine turbellarians
23
Platyhelminthes: Connecting nerves form a “_____________” pattern.
laddertype
23
Reproduction of most flatworm
Asexual and Sexual
23
Platyhelminthes: Their brain is a mass of ____________ arising anteriorly from the nerve
cords.
ganglion cells
23
In some turbellarians, yolk for nutrition of the developing embryo is
contained within the egg cell itself (____________), just as it is normally
in other phyla of animals
endolecithal
23
Platyhelminthes: The neurons are organized into ______, ______, and _______ types—an important advance in the evolution of nervous system
sensory, motor, and association
23
Many freshwater turbellarians can reproduce asexually by ________, merely constricting behind the pharynx and separating into two
animals, each of which regenerates the missing parts.
fission
23
In forms such as ______________ and ___________________ which are freshwater turbellarians, individuals do not separate at once but remain attached, forming chains of zooids
Stenostomum and Microstomum
23
Example of Freshwater turbellarians that has numerous mouths and pharynges
Phagocata
23
Flukes reproduce asexually in their ____ intermediate host
snail
24
some tapeworms, such as ____________, can bud off thousands of juveniles
in their intermediate host.
Echinococcus
24
The Fertilization of platyhelminths is internal via _____ or_____
penis or cirrus
24
Most flatworms are ________(hermaphroditic) and practice___________
-monoecious
- cross-fertilization.
25
Turbellarians are mostly free-living worms that range in length from
5 mm to nearly 50 cm.
25
Turbellarians: Their mouth is on the_________ and leads into a gut with a variable
form.
ventral side
26
The orders within class Turbellaria are distinguished by the
1. form of the gut (present or absent; simple or branched; pattern of branching)
2. the pharynx (simple; folded; bulbous)
26
have a folded pharynx and a gut with
many branches.
Polyclads (order Polycladida)
27
Polyclads include many marine forms of moderate to large size (_______________), and a highly _______intestine is correlated with
larger size in turbellarians.
-3 to more than 40 mm
-branched
27
Members of order ____________, which are ectolecithal and include
freshwater planaria, have a three-branched intestine.
Tricladida
28
Others turbellarians move by gliding, with the head slightly raised, over a slime
track secreted by the __________
marginal adhesive glands
28
Turbellarians are typically ____________ that combine muscular with
ciliary movements to achieve locomotion (much in the manner of a
snail).
creeping forms
29
Very small planaria swim by means of their _________
cilia
30
Some turbellarians have simple life cycles without a_________
distinct larval stage.
30
In some freshwater planarians, __________are attached by little
stalks to the undersides of stones or plants, and embryos emerge as
juveniles that resemble miniature adults.
egg capsules
30
Marine turbellarians have a _________ that is very similar to the trochophore of some annelids, molluscs, and members of other
phyla
ciliated larva
31
Body Structure of Turbellarians
-Bilateral symmetry and dorsoventrally flattened (flat from top to bottom).
-Unsegmented body
32
Digestive System of turbellarians
Incomplete digestive system: only one opening (mouth), no anus.
33
Nervous system of Turbellarians
-Ladder-like nervous system with a pair of cerebral ganglia (primitive
brain).
-Two or more nerve cords running longitudinally.
-Simple eye spots (ocelli) in some species to detect light
34
Feeding and Nutrition of Turbellarians
-Carnivorous or scavengers.
-Feed on small invertebrates, protozoans, or detritus.
-Capture prey with a muscular, extendable pharynx
35
Some species (e.g., Planaria) are famous for
their ability to ___________—cut one in half and it can regenerate into two.
regenerate lost body parts
36
Used frequently in biological research for studies on regeneration and
development
Species under turbellarians
36
Examples of Turbellarians: freshwater, often used in labs.
Planarians
37
Examples of Turbellarians: common genus in freshwater environments.
Dugesia
37
Examples of Turbellarians: marine flatworm that lives commensally on horseshoe
crabs.
Bdelloura
38
Examples of Turbellarians: marine acoels, often studied for symbiosis with
algae
Convolutriloba
39
-are all parasitic flukes, and as adults they are almost all
endoparasites of vertebrates.
-They are chiefly leaflike in form and are structurally similar in many
respects to more complex Turbellaria.
-A major difference is the tegument
Class Trematoda
39
Sense organs in class Trematoda are __________
poorly developed
39
Trematoda: Other structural adaptations for parasitism are apparent:
-various penetration glands or glands that produce cyst material
-organs for attachment, such as suckers and hooks
-increased reproductive
capacity
39
Of the three subclasses of Trematoda, two are small and poorly
known groups, but __________ (Gr. dis, double, + genos, descent) is a
large group that includes many species of medical and economic
importance.
Digenea
40
With rare exceptions, digenetic trematodes have a complex life cycle the
first host (intermediate host) being a ________and the final host (definitive
host) being a _______.
-mollusc
-vertebrate
41
Trematoda: A _____________ is one in which the parasite reproduces sexually. In some
species, a second, and sometimes even a third, intermediate host
intervenes
definitive host
42
The group has many species, and they can inhabit diverse sites in their
hosts: all parts of the digestive tract, respiratory tract, circulatory system,
urinary tract, and reproductive tract.
Class Trematoda
43
Typical life cycle of Class Trematoda include:
1. Adult
2. Egg (Shelled embryo/miracidium)
Inside the intermediate host:
4. Miracidium
5. Sporocysts
6. Redia
Outside the Intermediate host:
7. Cercaria
8. Metacercaria (inside second intermediate host)
43
Trematode: free-swimming, ciliated larva
miracidium
43
is the most important
liver fluke of humans and is common in China, southern Asia, and
Japan.
Clonorchis
43
Trematoda: When the fish is eaten raw, the juveniles migrate up the bile duct to
mature and may survive there for ________
15–30 years.
43
Blood Flukes
genus Schistosoma
44
an infection with blood flukes of genus Schistosoma
(Gr. schistos, divided, + soma, body), ranks as one of the major
infectious diseases in the world, with 200 million people infected.
Schistosomiasis
44
Trematode: lives in venules draining the large intestine;
Schistosoma mansoni
45
Trematode: localizes more in venules draining the small intestine
Schistosoma japonicum
46
Blood flukes differ from most other flukes in having separate
males and females
46
Trematode: lives
in venules draining the urinary bladder.
Schistosoma haematobium
46
Trematode: In each species, many eggs released by female worms do not find their way out of
the body but lodge in the liver or other organs, where they are sources of ___________
chronic inflammation
46
Trematode: Cercariae of several genera whose normal hosts are birds often
enter the skin of human bathers in their search for a suitable
bird host, causing a skin irritation called ___________
“swimmer’s itch”
46
General Life Cycle Stages of Trematoda includes:
-Definitive host (usually vertebrates)
-Intermediate host (Mollusc; snails)
46
Example Tremarode:
Common name: Blood Fluke
Hosts: Human; Snails
Disease: Schistosomiasis
Schistosoma mansoni
46
Example Tremarode
Common name: LiverFluke
Hosts: Sheep/Cattle/humans; snails
Disease: Fascioliasis
Fasciola hepatica
46
Example Tremarode:
Common name: Chinese liver fluke
Hosts: Human; Snails; Fish
Disease: Clonorchiasis
Clonorchis sinensis
47
Example Tremarode:
Common name: Lung Fluke
Hosts: Human; Snails; Crustaceans
Disease: Paragonimiasis
Paragonimus wstermani
47
-traditionally an order of
Trematoda, but they are now a separate class.
-Cladistic analysis places them as the sister taxon to Cestoda.
Class Monogenea
48
Body of monogeneans is covered with
Syncytial tegument
48
Monogeneans are mostly external parasites that clamp onto the gills and external surfaces of fish using a hooked attachment organ called an
opisthaptor
48
Monogeneans have body that are __________________ shaped
Dorsoventrally flattened and leaf- or elongated-shaped
48
Size of Monogeneans ranges from
0.33 mm to 20 mm
49
Monogenea: anterior sucker or adhesive organ.
Prohaptor
50
Monogenea: highly developed posterior attachment organ with hooks, clamps, or suckers—used to firmly attach to the host
Opisthaptor
51
The life cycles of monogeneans are simple, having a ____________ as
suggested by the name of the group, which means “single descent.
single host,
51
Monogenean reproduction
Hermaphroditic (cross-fertilization is common)
51
Reproduction in monogeneans is often very rapid, especially in ___________________—
leading to population explosions under suitable conditions
viviparous species
51
Unlike trematodes and cestodes, monogeneans have a _________
direct life cycle (no intermediate host)
51
Class Monogenean life cycle
1.Adult monogenean lives on a fish.
2.Produces eggs (in oviparous species) or gives birth to live young (in
viviparous species like Gyrodactylus).
3.Egg hatches into a ciliated larva called an oncomiracidium.
4.Oncomiracidium swims and finds a suitable host.
5.Attaches using haptors and develops into an adult
52
Monogenean infestations (called ___________)
monogeneiasis
52
monogeneiasis can cause:
* Gill damage → respiratory stress in fish.
* Weight loss, reduced growth.
* Increased mortality, especially in aquaculture.
* Not harmful to humans directly, but economically important parasites in
commercial fish industries
53
Tapeworms entirely lack a ____________,
but they have well-developed muscles, and
their excretory and nervous systems are
somewhat similar to those of other
flatworms.
digestive system
53
Examples of Monogenea
Host: Salmon, trout
Notes: Viviparous; important in aquaculture
Gyrodactylus
53
Examples of Monogenea
Host: Freshwater fish
Notes: Common gill parasites
Dactylogyrus
53
Examples of Monogenea
Host: Frogs
Notes: Inhabits urinary bladder of amphibians
Polystoma
53
Cestoda: The ________ is the organ of
attachment.
Scolex
53
Examples of Monogenea
Host: Freshwater fish
Notes: Two individauls fuse permanently in a cross-shaped form
Diplozoon
53
differ in many respects from the preceding
classes: they usually have long, flat
bodies composed of a scolex, for
attachment to the host, followed by
many reproductive units or
proglottids
Class Cestoda (Tapeworms)
54
Cestoda have no _________________, but
sensory endings in their tegument are
modified cilia
no special sense organs
54
Cestoda reproductive units
Proglottids
54
As in Monogenea and Trematoda, adult cestodes have no external,
motile cilia, and the tegument is composed of a __________________beneath the superficial layer of muscle
distal cytoplasm with sunken cell bodies
54
In contrast to monogeneans and trematodes, however, Cestode entire
surface is covered with minute projections called ___________ which are similar in certain respects to microvilli of the
vertebrate small intestine
microtriches (sing., microtrix),
54
These microtriches greatly ____________ of the tegument, which is a vital adaptation for a tapeworm, since it must absorb all its
nutrients across the tegument
amplify the surface area
55
Tapeworms are nearly all monoecious. The
main body of a cestode is a chain of proglottids
called a ____________
strobila
55
Typically, new proglottids form at a
_____________ just behind the scolex
(proximal to it).
germinative zone
56
A proglottid is usually fertilized by ____________in the same or a
different strobila
another proglottid
57
Shelled embryos form in the uterus of the proglottid, and either they are
expelled through a ________________ detaches from the worm as it reaches the distal end
uterine pore, or the entire proglottid (gravid proglottid)
58
Common cestode infecting humans: Beef tapeworm
Taenia saginata
59
Common cestode infecting humans: Pork Tapeworm
Taenia solium
59
Common cestode infecting humans: Dwarf Tapeworm
Hymenolepsis nana
59
Common cestode infecting humans: Dog tapeworm
Dipylidium caninum
59
Common cestode infecting humans: Fish Tapeworm
Diphyllobothrium latum
60
Common cestode infecting humans: Unilocular hydatid
Echinococcus ganulosus
61
Common cestode infecting humans: Multilocular hydatid
Echinococcus multilocularis
61
Cestode: Juvenile in flour beetles
Dwarf Tapeworm
61
Cysts of Juvenile in humans, infection by contact with dogs, common wherever humans are in close relationship with dogs and ruminants
Unilocular hydatid
62
Cysts of Juvenile in humans, infection by contact with fox, less common than unilocular hydatid
Multilocular hydatid
62
Taenia saginata: The six-hooked larvae (________) hatch, burrow into blood or lymph vessels, and migrate to skeletal muscle, where they encyst to become “bladder worms”
(_________)
-oncospheres
-cysticerci
62
people who live with, or contact, other people infected with taenia solium may
develop _____________, a serious disease caused by ingesting the fertilized eggs directly, without any intermediate host
cysticercosis
63
Taenia saginata: Adult worms may attain a length of______________, folded back and forth in the host intestine
7 m or more
