Platyhelminthes

Question 1

Two major evolutionary advances of plathyhelminthes

Answer 1

⚬ Cephalization
⚬ Primary bilateral symmetry

Question 2

General Features of plathyhelminthes

Answer 2

• Mesoderm well-defined
• Triploblastic
  *Highly specialized parasites
• Some argue this group were derived from complex
  free-living organisms

Question 3

having a body derived from three embryonic cell layers

Answer 3

Triploblastic

Question 4

the concentration of sense organs, nervous control, etc., at the anterior end of the body, forming a head and brain, both during evolution and in the course of an embryo’s development.

Answer 4

Cephalization

Question 5

Typical animals that have only one internal space, the digestive cavity

Answer 5

Acoelomates

Question 6

• Commonly called flatworms
• Vary from a millimeter to many meters in length
• Some free-living; others parasitic

Answer 6

Phylum Platyhelminthes

Question 7

Platyhelminthes is divided into four classes:

Answer 7

Class Turbellaria
Class Trematoda
Class Monongenea
Class Cestoda

Question 8

Class
⚬ Mostly free-living
⚬ Range from 5 mm to 50 cm long
⚬ Except for polyclads
Simple gut or no gut and a simple pharynx

Answer 8

Class Turbellaria

Question 8

free-living in Class Turbellaria Except for

Answer 8

polyclads, endolecithal
turbellarians

Question 9

Class Turbellaria organisms that have a folded pharynx and a gut with many branches

Answer 9

Polyclads

Question 10

Class Turbellaria is a Member of

Answer 10

Tricladidia

Question 11

are parasitic flukes
Most adults are endoparasites of vertebrates
They resemble ectolecithal turbellaria but the tegument lacks cilia in adults
Sense organs are poorly developed

Answer 11

Class Trematoda

Question 12

Adaptations for Class Trematoda parasitism include:

Answer 12

⚬ Hooks and suckers for adhesion
⚬ Increased reproductive capacity

Question 13

Phylum Platyhelminthes
* Adult fluke lives in bile passageways in the liver of sheep and other ruminants
* Eggs are pass out in feces

Answer 13

Fasciola hepatica (Sheep Liver Fluke)

Question 14

Phylum Platyhelminthes
In Fasciola hepatica (Sheep Liver Fluke), the ____ hatch and penetrate snails to become sporocysts

Answer 14

Miracidia

Question 15

two generations of rediae

Answer 15

Cercaria
metacercariae

Question 16

stage that encyst on vegetation and await being eaten by sheep in Fasciola hepatica (Sheep Liver Fluke),

Answer 16

Cercaria

Question 17

stage that develop into young flukes
in Fasciola hepatica (Sheep Liver Fluke),

Answer 17

metacercariae

Question 18

Phylum Platyhelminthes
* Most important human liver fluke
* Common in China, Japan, and Southeast Asia
* Also infects cats, dogs, and pigs
* Adult fluke is 10–20 mm long with an oral and ventral sucke

Answer 18

Clonorchis sinensis: Chinese Liver Fluke

Question 19

Clonorchis Life Cycle

Answer 19

• Adults live in bile passageways of humans and other fish-eating mammals
• Eggs containing a complete miracidium are shed into water with feces
• The eggs hatch only when ingested by snails of specific genera
• Miracidium enters snail tissue and transforms into a sporocyst
• Sporocyst produces one generation of rediae, which begin differentiation

Question 20

Phylum Platyhelminthes
Over 200 million people infested with schistosomiasis
Common in Africa, South America, West Indies, and the
Middle and Far East
* Sexes are separate

Answer 20

Schistosoma: Blood Flukes

Question 21

• 3 species account for most human schistosomiasis

Answer 21

⚬ S. mansoni in venules of large intestine
⚬ S. japonicum in venules of small intestine
⚬ S. haemotobium in venules of urinary bladder

Question 22

Schistosoma Life Cycle

Answer 22

• Eggs discharged in human feces or urine
  *In water, eggs hatch as ciliated miracidia
• Must contact a particular species of snail to survive
  *In the snail, they transform to sporocysts
• Sporocysts produce cercaria directly
• Cercariae escape the snail and swim until they contact bare human skin
• Cercariae pierce the skin and shed their tails
• Enter blood vessels and migrate to the hepatic portal blood vessels
• Develop in the liver and they migrate target sites
• Eggs released by females are extruded through gut or bladder lining and exit with feces or urine

Question 23

Eggs that remain behind become centers of inflammation in Schistosoma

Answer 23

Trues

Question 24

Phylum Platyhelminthes that parasitizes humans, pigs, rodents, etc. Eggs are coughed up in sputum, then swallowed and eliminated in feces Human infection occurs by eating uncooked crabmeat

Answer 24

Paragonimus westermani: Lung Flukes

Question 25

Metacercariae of Paragonimus westermani: Lung Flukes develop in

Answer 25

freshwater crabs

Question 26

Cercariae of Paragonimus westermani: Lung Flukes shed into the water and ingested by

Answer 26

freshwater crabs

Question 27

Paragonimus westermani: Lung Flukes Life Cycle

Answer 27

*Eggs are coughed up in sputum, then swallowed and eliminated in feces *Zygotes develop in water and miracidia penetrate a snail host *Within the snail, miracidia give rise to sporocysts, which develop into rediae * Cercariae are shed into the water and ingested by freshwater crabs * Metacercariae develop in freshwater crabs *Human infection occurs by eating uncooked crabmeat

Question 28

Monogenetic flukes were originally placed in Trematoda External parasites of fish especially gills, but a few are found in bladders of frogs and turtles Have direct life cycle in a single host

Answer 28

Class Monogenea

Question 29

* Some now argue they are sister taxa, Trematoda and Monogenea having a posterior attachment with hooks

Answer 29

true

Question 30

Class Monogenea part that attaches to host by posterior hooks

Answer 30

Oncomiracidium

Question 31

Class Monogenea Posterior hooks may become the posterior attachment organ of the adult, the vary widely (hooks, suckers, clamps) Withstand the force of water flow Some serious economic problems in fish farming

Answer 31

opisthaptor

Question 32

have long flat bodies with scolex Lack a digestive system Muscles, excretory and nervous systems similar to other flatworms Lack sensory organs except for modified cilia

Answer 32

Class Cestoda Tapeworms

Question 33

Class Cestoda Holdfast structure with suckers and hooks

Answer 33

scolex

Question 34

Class Cestoda Scolex is followed by a linear series of reproductive units or

Answer 34

proglottids

Question 35

Class Cestoda the long body of the Tapeworms

Answer 35

strobila

Question 36

Class Cestoda * Lives as an adult in the alimentary canal of humans * exists in beef * Mature adults can reach over 10 meters in length with over 2000 proglottids * Scolex has four suckers but no hooks Gravid proglottids pass in feces *no suckers

Answer 36

Taenia saginata: Beef Tapeworm

Question 37

Taenia saginata: Beef Tapeworm *Juvenile form found in

Answer 37

intermuscular tissue of cattle

Question 38

each segment in the strobila of a tapeworm, containing a complete sexually mature reproductive system.

Answer 38

proglottids

Question 39

segment that contains uterine branches filled with eggs, or shelled infective larvae

Answer 39

Gravid proglottids

Question 40

Taenia saginata Life Cycle

Answer 40

* Cattle swallow shelled larvae that hatch as oncospheres *Oncospheres use hooks to burrow through the intestinal wall into blood or lymph vessels * When they reach voluntary muscle, they encyst to become bladder worms (cysticerci) * When the infected meat is eaten, the cyst wall dissolves and the scolex evaginates to attach to intestinal mucosa *New proglottids develop in 2–3 weeks *Infected individuals expel numerous proglottids daily *Infection can be avoided by eating only thoroughly cooked beef

Question 41

Phylum Platyhelminthes * Adults live in small intestine of humans * found in pork * Scolex has both suckers and hooks on the rostellum

Answer 41

Taenia solium: Pork Tapeworm

Question 42

Phylum Platyhelminthes *Juveniles live in muscles of pigs

Answer 42

Taenia solium: Pork Tapeworm

Question 43

If eggs or proglottids of Taenia solium: Pork Tapeworm are ingested what happens

Answer 43

⚬ Embryos migrate to organs and form cysticerci

Question 44

commonly occurs in eyes or the brain blindness, serious neurological symptoms or death, caused by Taenia solium: Pork Tapeworm Infection can be avoided by eating thoroughly cooked pork

Answer 44

Cysticercosis

Question 45

Phylum Platyhelminthes Adults found in intestines of humans, dogs, cats and other mammals Immature stages found in crustaceans and fish Largest cestode of humans, reaching up to 20 meters in length

Answer 45

Diphyllobothrium latum: Fish Tapeworm

Question 46

Phylum Platyhelminthes * Adults parasitize dogs and other canines *Juveniles infest many mammals *Humans may serve as intermediate host * Main cyst maintains a single chamber ⚬ Daughter cysts bud off with thousands of scolices, each able to produce a worm if eaten * Surgical removal is the only treatment

Answer 46

Echinococcus granulosus: Unilocular Hydatid

Question 47

Echinococcus granulosus: Unilocular Hydatid Juveniles are a special cysticercus, a hydatidcyst, that grows for up to

Answer 47

20 years

Question 48

Neodermatans are composed of

Answer 48

trematodes, monogeneans, and cestodes

Question 49

taxon Turbellaria is paraphyletic

Answer 49

true

Question 50

Neodermatans form a monophyletic group

Answer 50

true

Question 51

Allied with trematodes, monogeneans, and cestodes as the sister group to endolecithal turbellarians

Answer 51

Ectolecithal turbellarians

Question 52

phylum Considered a “missing link” between protozoa and metazoa Have a simple level of organization Minute, ciliated, and wormlike animals

Answer 52

Phylum Mesozoa

Question 53

Phylum Mesozoa All live as parasites in

Answer 53

marine invertebrate

Question 54

Phylum Mesozoa Most composed of only ________ cells arranged in two layers Layers are not homologous to germ layers of other metazoans

Answer 54

20 to 30

Question 55

Phylum Mesozoa Two classes

Answer 55

Rhombozoa and Orthonectida

Question 56

Phylum Mesozoa * Live in kidneys of benthic cephalopods *Inner, reproductive cells give rise to vermiform larvae * When overpopulated,reproductive cells develop into gonad-like structures producing male and female gametes * Larvae are shed with host urine into the seawater

Answer 56

Rhombozoans

Question 57

Rhombozoans Adults called ________ and are long and slender

Answer 57

vermiforms

Question 58

Phylum Mesozoa * Parasitize variety of invertebrates * Reproduce sexually and asexually * plasmodium

Answer 58

Orthonectids

Question 59

Orthonectids Asexual reproduction consists of a multinucleated mass called a

Answer 59

plasmodium

Question 60

Some consider these organisms primitive flatworms and place them in phylum Platyhelminthes

Question 61

Molecular evidence groups Phylum Mesozoa with flatworms in

Answer 61

superphylum Lophotrochozoa

Question 62

orthonectid and two species from a rhombozoan subgroup, the dicyemids, did not show members of the two classes to be

Answer 62

sister taxa

Question 63

Phylum Mesozoa may not be monophyletic

Answer 63

true

Question 64

*Often called ribbon worms *Have a long muscular tube, the proboscis *Over 1000 species * Most are less than 20 cm long *General body plan similar to that of turbellarians * Epidermis is ciliated with many gland cells * Excretory system has flames cells; several have rhabdites * Mostly dioecious

Answer 64

Phylum Nemertea

Question 65

long muscular tube in Phylum Nemertea

Answer 65

proboscis

Question 66

Phylum Nemertea wjay is the shape of their pilidium larva

Answer 66

Helmet-shaped pilidium larva

Question 67

* Adult has an anus, producing a complete digestive system that is more efficient * Simplest animals with a blood-vascular system * Most are marine ⚬ Some are found in moist soil and freshwater * Few are commensals or parasites

Answer 67

Phylum Nemertea

Question 68

Ventral mouth but no anus resembling flatworms and trochophore larvae of annelids and molluscs

Answer 68

pilidium larva

Question 69

regenerate readily * Some fragment themselves during certain seasons * Tail sections can regenerate a new proboscis within a short time

Answer 69

Phylum Nemertea

Question 70

Phylum Nemertea Classes

Answer 70

Class Enopla Class Anopla

Question 71

Phylogeny of Nemertea

Answer 71

* Much debate about the phylogenetic position of nemerteans * Larval forms vary *Nemertean body plan is controversial * Are they coelomate or acoelomate?