Helminthes- Trematode Intro

Question 1

What is the most common niche for helminthes in humans?

Answer 1

in the GI tract, as adults. They are one of the most prevalent forms of parasitic disease

Question 2

By which two general means do helminthes do damage to the host?

Answer 2

through physical and chemical damage

Question 3

What are the three groups of helminthes?

Answer 3

cestodes (tapeworms), trematodes (flukes), and nematodes (roundworms)

Question 4

Which group of helminthes has proglottids that are each hemaphroditic?

Answer 4

cestodes

Question 5

Which group of helminthes are all hemaphrodites with one exception?

Answer 5

all trematode species except schistosomes

Question 6

Which group of helminthes are dioecious?

Answer 6

nematodes

Question 7

Which groups’ bodies are covered by tegument?

Answer 7

cestodes and trematodes

Question 8

Which group’s bodies are covered by cuticle?

Answer 8

nematodes

Question 9

Which group lacks a digestive tubule?

Answer 9

cestodes

Question 10

Which group’s digestive tubule ends in a cecum?

Answer 10

trematodes

Question 11

Which group’s digestive tubule ends in an anus?

Answer 11

nematodes

Question 12

How are digenetic trematodes classified?

Answer 12

by the organ that they invade

Question 13

Where do blood flukes invade?

Answer 13

the vasculature of the GI or genitourinary systems

Question 14

Where do intestinal flukes invade?

Answer 14

the lumen of the GIT

Question 15

Where do live flukes invade?

Answer 15

the liver

Question 16

Where do lung flukes invade?

Answer 16

lungs and sometimes other organs such as the CNS

Question 17

What is a distinguishing feature of the trematode classification?

Answer 17

all trematodes are obligate parasites in all classes of vertebrates

Question 18

What does digenetic mean?

Answer 18

the life cycle involves at least 2 hosts

Question 19

What is the first intermediate host?

Answer 19

a mollusk, usually a snail

Question 20

What is the definitive host?

Answer 20

a vertebrate

Question 21

What is the name of the third host?

Answer 21

most trematodes have a second intermediate host

Question 22

Where do the larval stages most often occur?

Answer 22

in the intermediate host(s)

Question 23

Where do the adult stages most often occur?

Answer 23

in the definitive host

Question 24

Where is the oral sucker located and what is its function?

Answer 24

at the anterior end of the trematode and is used for attachment and feeding

Question 25

Define acetebulum

Answer 25

aka ventral sucker. located mid-ventral to oral sucker, has no internal opening, used for attachment only

Question 26

What is the syntegument?

Answer 26

the outer layer of the tegument body covering. contains mitochondria, secretory bodies and occasional spines. covered by a chemical layer

Question 27

What is cytotegument?

Answer 27

cells beneath syntegument that produce mucus. separated from syntegument by tegumental muscle and connected by cytoplasmic bridges

Question 28

What are the functions of the tegument?

Answer 28

1) osmoregulation & excretion 2) synthesis & secretion of mucus 3) absorption of nutrients

Question 29

Describe the trematode digestive tract

Answer 29

food enters mouth and passes into the esophagus, which separates into two long blind-ending cecum (no anus)

Question 30

Define parenchyma

Answer 30

loosely arranged cells filling space between internal organs

Question 31

What is the function of the excretory system?

Answer 31

removes excess water that has diffused into the worm

Question 32

What are flame cells and how do they function?

Answer 32

cells with beating flagella that create hydrostatic pressure to draw water from parenchyma into the collecting duct. The collecting ducts empty into the excretory bladder at the posterior end

Question 33

Describe the nervous system of trematodes

Answer 33

Ladder-type system: anterior ganglion + lateral nerve trunks + connecting commissures. Sense organs in the tegument

Question 34

Which two ways can hermaphroditic trematodes reproduce?

Answer 34

via auto-fertilization OR require another worm for cross-fertilization (even though they are hermaphroditic)

Question 35

What are the components of the male reproductive system?

Answer 35

two testes -> sperm ducts (2 vas efferentia join to form vas deferens) -> cirrus sac

Question 36

What are the components of the female reproductive system?

Answer 36

SINGLE ovary produces eggs -> oviduct -> ootype

Question 37

Describe trematode eggs

Answer 37

well developed egg shells, usually operculate (having a lid) except in schistosomes (have spines)

Question 38

When and what happens when the egg hatches?

Answer 38

release of operculum. | can happen when ingested or under certain environmental conditions

Question 39

What distinguishing organ do most miracidium have?

Answer 39

cilia used for locomotion

Question 40

What do the miracidium do?

Answer 40

free-swimming stage that either seeks the intermediate host OR, in a few cases, is not free-swimming and hatches in the intestine to invade mollusk tissues

Question 41

What marks the transformation of the miracidium to mother sporocyst?

Answer 41

at the point of penetration where cilia, penetration glands and apical gland are lost

Question 42

What is the sporocyst cell and what does it become?

Answer 42

a hollow fluid filled germinal sac containing germ cells. | the germ cells either multiply & develop into daughter sporocysts or into a second larval stage (redia)

Question 43

How does the sporocyst obtain nutrients?

Answer 43

passage of soluble material across the tegument

Question 44

Can a trematode have both a daughter sporocyst and redia stage?

Answer 44

NO! if there is a daughter sporocyst stage, there is no redia stage and vise versa

Question 45

What are the distinguishing features of redia larvae?

Answer 45

more active form, has a simple gut (mouth + pharynx + simple intestine), may have a ridge-like collar

Question 46

What is the ridge-like collar?

Answer 46

located behind the mouth. Below this, the birth canal opens and either a daughter redia or cercariae emerges

Question 47

What can redia prey on?

Answer 47

sporocysts & redia of the same species or of other species

Question 48

Describe the cercarial stage

Answer 48

infective stage. variations in structure depending on species. usually free-swimming form. Has a brief free-living stage. At this point may penetrate the next host or be ingested.

Question 49

What is the mesocercaria?

Answer 49

the stage where the cercaria enters a second intermediate host (3-host system)

Question 50

What is the metacercaria?

Answer 50

encysted form where the mesocercaria's second intermediate host is ingested by a third intermediate host

Question 51

What are the potential final intermediate hosts?

Answer 51

a fish, an arthropod, another mollusc (usually an echinostome)

Question 52

How does the cercaria/metacercaria enter the definitive host?

Answer 52

can be ingested with the intermediate host by a carnivore definitive host OR ingested in encysted form when on plants by a herbivore definitive host